If an other company offer XX% more than your current company but you stay for your "friends" you could have a big disappointment in the future.
The majority of my closest friends (and their closest friends) are people that started from work relationships and we have had no problem leaving those companies when the time came, and we have maintained our friendships. It’s not any different than any other friendship where people sometimes move or start new hobbies.
That said, if someone does choose to stay at a specific company because they have friends there... so what? Having a strong social circle and support network is, in many cases, a better reason to work at a company than a higher paycheck.
In the US your healthcare and well-being are pretty much dependent on your job. And make no mistake, this is 2020, where your org will fire you for any reason so long as it makes sense to an MBA. As your sole source of income and healthcare they wield immense power in your life, and any interactions you have with coworkers or other work-related engagements are going to revolve around that power disparity in some way. Sure there are freelancers and well paid devs who can come and go as they please, but those are a tiny minority compared to all of those who are thusly constrained.
Point is, don't make work your social life cuz when they fire your ass you're going to lose your support network AND your meal ticket.
1) This is a self fulfilling prophecy. It's no secret that when it comes time to let people go (or time to promote), managers (even the MBA boogeymen) will stick their neck out for people they like more than for people they do not know. If you're continuously being dropped like a hot rock by your employers and you don't think it's because of performance reasons, perhaps you should reconsider your work relationship habits.
2) What's with the notion that you "lose your support network" just because you get fired? There is no reason that you should stop being friends with people just because you lose your job, even if those friendships stemmed from your workplace. I understand that it may be more difficult to find the time to socialize with them if you are not at work with them (which is exactly why it's worth it to go to those "forced beer nights" and build a relationship outside the context of work), but that doesn't mean you should stop putting in the effort and cut ties entirely.
Even if you are entirely career focused, getting fired is a situation in which you should actually lean heavier on your support network, especially coworker friends, as they are the ones that most likely can do the most to help you find a replacement job.
I really don't see the issue in socialising with colleagues and potentially becoming friends.