Apart from the other reasons people have mentioned - the headline “we switched from postgres to $database (for example MySQL) is so unusual it warrants a justification. PG is so good that you really need to be a very niche case for there to be objective reasons to do such a switch. And granted the bigger the company the more intricate and unique its requirements.

I personally advise people to just start with PG and if they encounter very unique requirements that for some reason PG can’t be tuned to - then do the switch.