Or some differences in gear spacing. I’m not an expert in it, but tried my best to summarize a succinctly as possible

There’s surprisingly a fair bit of overlap on the gear ratios of a 2 or 3x that makes a 1x11 or 12 have a similar range of ratios. However you do have to sacrifice either a bit of top end speed or climbing ability so you see a few more 2x on road bikes. I’ve never found myself wanting more from my 1x mtb drivetrain