Alts have their purpose, primary of which is to extract the most value out of whatever bitcoin you put into it, as, let's face it, most altcoins are paired with bitcoin on exchanges and almost nothing else.
They are the penny stocks of the crypto world.
As one post in 2016 or 2017 says, if an investor went in on the top 10 alts by marketcap with no regard to doing any other due diligence, he'd have made a lot more money than if he put the same fiat amount all in, in bitcoin. If he put it in bitcoin only, he'd make 8 to 9 times. If he "diversified" to the top 10 after bitcoin during that time, he'd make 100 to 200 times.
Let's just take ETH as an example, if you joined the ICO back in 2014, 1 BTC = 2000 ETH. ... Just remember to take your profits a few years later, but even if one did not, that ETH is still worth ... 40 times what BTC is worth today.
Like a lot of people, I looked at ETH, but did not participate. I looked at LTC, bought them at 20, sold them at 40 a week later, I think that was my best move then. I looked at EOS, ZCASH, DASH, I tried to join BAT but missed the deadline by 2 seconds or whatever it took to finish that one (crazy ico times) ... then I looked a bunch of smaller cap altcoins, and would have made some profits if we knew to cash them out in early 2018.
Of course, that's not fair and we don't have crystal balls, but we should have seen the so called crypto winter coming anyway.
Now, stablecoins are here, so it's either that or sell the alts to get BTC, eventually keep a large percentage in BTC, either to use or to just hodl.
If you're watching the regular stock market, I'd say altcoins are like the "Beyond Meats" ... you start at 70, pump up to 200, then it's now back to 70, and likely to go down, down, down.
This is a classical analogy and good example too.
I want to go down to your last paragraph briefly. It is better to convert shit coins to btc but the issue is, after you calculate the value, they still amount to nothing and can't come out from exchange because of fees
. I have learnt my lessons with pump and dump shit coins.