Internet Explorer is the most popular web browser and everybody knows about it, and it's everybody's first browers, bla bla bla
In case of a browser, you can use Internet Explorer, or Mozilla Firefox. Or Google Chrome. Or Safari. You have a choice. And if you create a website, then you don't have to change your hosting provider, if you want to switch your browser.
When it comes to cryptocurrencies, then you cannot hold both BTC and LTC, at the same time, with the same amount. You cannot have $1000 in "crypto", and decide, that "today, it is $500 in BTC, and $500 in LTC". And tomorrow, if you change your mind, then you cannot instantly say "now I signed this message, so now I pick $700 in BTC, and $300 in LTC, and want to use it in that way". You have to make a transaction, and pay some fees. Which means, that changing your choices, creates additional costs, which can very easily become a bottleneck, because you don't have "just $1000 in crypto". You have to pick something, and stick with that choice. And as long as it is the case, and as long as altcoins create completely separate monetary bases, you have to pick only "this coin or that coin". You cannot have both BTC and LTC, on the same UTXO.
So, it is more similar to the situation, where you have some EXE file, and you want to switch from Windows to Linux or MacOS. Of course, there is Wine project. But: it took many years for people, to get there. And still, there are many cases, where a particular EXE file works only under Windows, and nowhere else. And then, you are forced to use Windows, even if you don't want to.
And then, the comparison is even more fair, if you pick "x86 vs ARM vs M1 vs AVR", and so on. Because then, if you have your EXE, and you want to run it somewhere else, then you still need a compatibility layer, like a virtual machine, or a transcompiler, which will translate all of that, opcode by opcode. Then, you really have to "abandon EXE, to have ELF", just like you have to "abandon BTC, to have LTC". You cannot use both, at the same time, just like you can visit bitcointalk from two different browsers.
But the only "1000x" opportunities out there will be from digital currencies that change the paradigm
I think people need more features on existing coins, and not just more coins. If your strategy is "please sell your BTCs, and buy my product", then many people will not do that, because they know the history. I guess a lot of BCH users would really want to have 1:1 peg with BTC today. Now, after 7 years, it is clear, that those, who stayed with BTC, simply won.
And also, this "1000x" stick has two ends: there is of course a chance for 1000x gains, but there is also a chance for 1000x losses. And if you are not an altcoin creator, then you usually are on the losing side, when altcoin makers simply cash out into BTCs, and leave naive investors behind. It happened too many times in the crypto world, so wise people have many reasons, to worry about that kind of scenario (and not that many examples of 1000x gains, to really believe, that this particular altcoin is the unicorn).