Because you don't seek a real answer, you seek an answer that you want to hear and you dismiss everything else because you don't like it.
Nope - it's because it does not answer my question. What you and most other people in the thread here do is explain how the current market works, not why this is how a proper market should work, and why it makes sense that the price of BTC basically dictates the prices of every other asset.
Let me try with another example.
Suppose - BTC is a steam train, that revolutionized hitherto horse-drawn transportation. A marvelous feat of engineering.
Suppose further that alt-coins are airplanes, ships and trucks.
In your case, I suspect you will say alt-coins are trains that run on spaghetti tracks and melt when it's too hot - that's fine, it doesn't matter.
What does matter is - each time there are supply problems with coal and the BTC train network has problems, the prices of air fares, shipyards and trucks also wildly jumps up and down. In your case, coal price rises cause havoc in the spaghetti rail business. When governments threaten to regulate those damn noisy train machines and shares in the steam train business dive, at the same time shares in airlines and shipping companies fall even more.
What I want to know, is how is this a healthy market? How does it make sense? Why should an event in the steam train business impact any other business at all? Maybe you don't like flying, or you get sea-sick on boats - OK, you don't have to like boats or airplanes... but why should developments in the train market impact those markets? Because that is basically the situation.
You are not sticking to the topic; I am not asking for a value judgment on the merits of alt-coins, or whether they are worth anything. I am asking you why a movement in BTC price should have any relationship with the price of alts. You talk about people having a choice, but the truth is that this choice is severely restricted and far less meaningful than it should be. The fact you evidently think investing in alts is a silly choice - that's fine
But all this is not relevant to the question.
Let me phrase it some other way still.
If I asked you - Stompix, I have invented a new type of asset, and I need you to come up with a design for how a market to trade these assets would work. You diligently get to work, and come up with a model for a market that makes sense.
I'd bet my life on it that the feature "prices of all assets are derived from and/or go up and down with the price of the top asset" would not be a part of that design. Yet, that is the current crypto market design.
For some people it doesn't make sense that the Earth is not flat, that doesn't change things, we're telling you what's happening in the markets and why this is happening, the fact that you don't want to accept the answers as rational doesn't mean the answers are not true.
That the earth is not flat is a fact that can be proven by empirical study. Your answers are correct (albeit slightly biased against alts) if the question was "Explain to me how the prices of alt-coins work in the current market design" - but that is not the question. I guess what I am trying to illustrate is that the way the market is operating right now is very far from reasonable or sensible; and again, you are totally free and at liberty to not give a s**t about alt-coins, that's totally cool. But surely even if you totally don't care about alts, you still gotta admit that the influence of the price of BTC on their value is absolutely without any merit.
Take game tokens, for instance, like MANA or ENJ. They have absolutely nothing to do with BTC. BTC could disappear tomorrow, nothing in their neck of the woods would change. Yet, if BTC price moves, so does theirs. This is ridiculous; in-game items don't suddenly become worth less or more, the games they are used in do not depend on BTC, BTC has nothing to say or add to those ecosystems. Yet it directly impacts tens of thousands of users as their tokens change in value for no reason that has anything to do with the economies of said tokens. And just to be clear - I don't hold any of those and personally don't care much for them, but I DO care about the broader crypto landscape that is basically "held hostage" by the fortunes of BTC. Surely, even if you think alt coins are nonsensical, even you should think that to be incorrect