Or... they have the time and knowledge to carefully consider it and just haven’t concluded that it has any benefit for some reason.
Not everyone who disagrees with you is doing so because they just haven’t thought about it hard enough yet.
They think it’s a great idea, and would love if they could do everything they do currently with FOSS, and no extra time-investment. But, with few exceptions, that’s rarely possible, especially as more and more computing happens on phones.
Of course, the people I speak to about FOSS are by no means wholly representative. But IME it’s that software freedom tends to end up being considered a nice idea but a very low priority, rather than an idea with no benefits.