1) The idea of sidechains is that many millions of relatively low-importance transactions could, and usually would, be aggregated into one bitcoin transaction. I might send one Bitcoin in one transaction to the sidechain peg of some sidechain dedicated to tipping. I would then perform micro-transactions within the sidechain to my heart's content. On the other side, a person being tipped would probably rarely bother to cash out into Bitcoin (or a different sidechain.)
This is not very different to what we have today with exchanges where huge amounts of trading happen 'off-chain'. A difference is that with a decent implementation I don't have to trust the sidechain and I can verify to a reasonable degree that this is so (just like with Bitcoin proper.) This is not at all the case with non-backed solutions and because of this they regularly steal and probably inflate the currency as well. The user basically sees a display transmitted out of a black box...an hears all kinds of marketing about how honest to operator is of course.
Ultimately all this does to Bitcoin is to make it seem like there are mostly large players doing important and high value transactions (and thus capable of paying generous transaction fees) where in reality a universe of people are reaping the rewards promised of a solution such as Bitcoin. This is no loss at all to Bitcoin and I think it is a giant benefit because trying to service the world's exchange economies cannot help but balloon the system to something which doesn't really resemble the original almost at all. Not only that, but a 'batch mode' system like Bitcoin is inherently disadvantaged for real-time operations as are most burger sales. Sure there are bandaids but they are kind of ugly in my opinion, and ultimately result in provoking the same non-trustless system constructs that we see in the current crop of non-backed off-chain providers.
2) Yes, 1 billion transactions is 1 billion transactions. The point is that there would be many many sidechains which I don't give two shits about. If I am acting as an infrastructure provider (by running a node or whatever) most of them don't effect me. I support the chains that I need and care about, and those which have not grown to a point that is uncomfortable for me. I'll be more than happy to support the Bitcoin core as well if I can. That's why I'm so keen to avoid having it bloat to the point where doing so is no longer realistic.
Edit: And because of the peg I don't have to worry about throwing money down a rat-hole when I choose what sidechains I like. If it fails I can get my money back (again, if properly implemented and I do my due diligence correctly.) That is one of the biggest reason I've not messed around with alts which, in principle, I've never had anything against even if they do draw interest/value away from Bitcoin. Sidechains give the benefits I like in well implemented alts without those two disadvantages.
3) Not sure what you are getting at with 'gift card' but in most mainstream implementations they are highly centralized...as are most mainstream things generally. Some sidechains might (and probably would) work on a sort of a token model. Those could be considered micro-gift cards of sorts, though simply one's footprint in the sidechain would also.
1) While I still don't see how this can work as great as you think it can (even if there were a trustless way to do it) unless all of the sidechains are cooperating and you can transfer directly between them, I'm also operating under the assumption that miners/processors in sidechains have income from fees as well. Ultimately, for bitcoin to get the same fees it would get otherwise, users would have to pay more to use sidechains so that the entities running the sidechains can make their money, too. Quite frankly, sidechains for transfer of value just don't seem likely to have benefits that outweigh their costs, but that is IMO.
2) I think sidechains for added benefits would be fine, but pruning and blocksize increases need implemented in bitcoin regardless.
3) I'm not sure what you're getting at in wanting sidechains instead of bitcoin or cash, so I'm shooting in the dark. Regardless, 0 confirm transactions are not a concern for small transactions, and waiting for confirmation is not a concern for large transactions, so I'm not sure what benefit you are looking for in sidechains (assuming pruning is implemented in bitcoin to address your [2]).
All of that having been said, I don't feel like we're arguing, but I don't feel like we're making headway in understanding each other, either, and I have no problem with this conversation dropping.
Actually, that's about the price he is currently paying due to credit card fees, it's just hidden so he doesn't know he's paying it.
Most of my BTC spendings
do receive discounts.
Well, good, and true in the online world, but I'm talking about stopping by a gas station. Some of them do give discounts for buying with cash, but the majority do not, and for established retailers that do not give a discount for cash, it seems unrealistic to expect a discount for bitcoin, especially if they are paying a processor, even if that processor costs far less than the credit card processor they use.