TBH, it's all about "trends". Many, many domain extensions have tried in the past to replace ".com" (dot com) and they all remained in a trend for some nice amount of time; however, dot com has always survived and outclassed them all repeatedly. Moreover, there's more of a "show-off" element involved in almost every new start-ups out there than the "cheaper extension" element. Generally, dot com is cheaper than dot io across all major domain name providers (Godaddy, NameCheap, etc), but interestingly, most people (especially the ones who're struggling with a new start-up) who think that they're "over-smart", try to go with the brand new shorter domain name (dot io, dot co, etc), even when the dot com version of the same name is available. I know about a few cases (and they were all start-ups) which started with a better-than-dot-com domain name and later migrated to dot com due to lack of SEO, lack of visitors' interaction with the website, etc.
It means investors have reasons to doubt about reliability of projects that run their sites on domain names with .io, .info, etc.
I'm not sure if someone around has witnessed the growth (and downfall) of paid-to-click industry (talking about the years 2005 to 2015), but I think that those who have witnessed it will still care about the domain name extension of the website before risking their valuable time (and in some cases, the funds) on the websites. I remember that in the years 2013-2015, a lot of PTC websites (which were literally run by 14-year-old kids) were popping up and due to lack of pocket-money, they were all going for a very cheap "dot info" domain name, which had a couple of bucks registration charges (and in some cases, it was even less than a buck, excluding that 18 cents ICANN fee). Resultantly, people stopped being interested at all in those dot info/dot tk platforms and were all considered as "child-owned" websites. I think that if BTC dominance continues to grow and alts continue to shrink, then we might get to see the kids popping up in crypto-industry and cloning the alts with a negligible budget. If that day comes, I'm sure that those kids will be then looking for those "under-a-buck" domain names again, and newcomers will have to stay away from those projects!
P.S. in those days, dot co domain name was considered to be rich (& a better/shorter version of dot com) and people used to trust the website using it more as compared to the websites using other extensions. So IMO, dot io is the new dot co these days.
.com is so 90's.
.io is for companies of the new millennium - internet organizations!
Hmmm... well, quite sure that my grandpa still thinks that all websites end up with .com extension (only).
