The problem is these companies almost universally could not exist without open source software that allowed them to commercialize things. It is impossible for the vast majority of companies to ever "give back" as much to open source as they profit off of it - from the Linux kernel, all the GNU stuff, the nginx or apache webservers hosting webpages and API access, the haproxy load balancers, the corosync/pacemaker they're using to keep things online, etc. etc. etc.
How many of these companies could exist if all these projects underpinning their own swapped to the SSPL, BSL, etc? And I don't mean now - once you reach a certain size, if you have to replace a bunch of dependencies, you have the resources to do it. But when these companies were smaller, would they have been able to create their own implementation of all these dependencies and still get their product to market? Would they have had the resources to commit to all of it? Would they have had the money to pay for non-FOSS options?
How many of these projects would still exist if the community couldn't commercialize them? We're not even talking about whether or not they ultimately end up contributing code back, etc., because it's not like these licenses give you some threshold of code contribution after which you can commercialize it. Sure, the possibility exists of some special private licensing agreement being struck, but that's possible with proprietary code, too.
Source available might sound fine from a personal use perspective, but it ignores the fact that the environment that made all of this possible would not have been possible under that model.