My recollection from working at a tech company in the early 2010s is that renting rack space and building servers was expensive and time consuming, estimating what the right hardware configuration would be for your business was tricky, and scaling different services independently was impossible. also having multi regional redundancy was rare (remember when squarespace was manually carrying buckets of petrol for generators up many flights of stairs to keeps servers online post sandy?[1]).
AWS fixed much of that. But maybe things have changed in ways that meaningfully changes the calculus?
[1] https://www.squarespace.com/press-coverage/2012-11-1-after-s...