You're very lucky. My first computer was an old Dell that my parents were planning to throw away (as it was slow) but which I rescued and, whilst looking for ways to speed it up, stumbled across Ubuntu. That's how, aged 13, I first got into Linux. If we had been using computers with secure boot, I assume I would still have gotten involved with computers, but quite possibly at a much later stage and I highly doubt I would be at the same level I am now.

Plus, it's hard enough to get people to switch to Linux now as it is - telling people they need to buy new computers, that'll reserve Linux purely for geeks at a time when it is starting to appeal more and more to consumers (though admittedly, not quite there yet).