Your correct that a huge amount of software today uses libraries that are distributed under some form of libre licensing although in most cases this is LGPL , BSD or Apache style licenses rather than GPL.
Sure perhaps they run some stuff on a GNU/Linux server but in most cases this could just as easily be a BSD , Solaris or even Windows server.
There are many types of software where GPL is absolutely a barrier , namely just about anything where the software is the end product. For example pretty much any video game or for example Adobe Photoshop/Illustrator. Some products simply don't lend themselves well to selling support , very few people are going to pay $1/min to get help running a program that is simple enough to figure out on their own from reading the manual and that should 99% of the time just install and run especially if it's not something mission critical that requires 6 nines uptime.
> Sure perhaps they run some stuff on a GNU/Linux server but in most cases this could just as easily be a BSD , Solaris or even Windows server.
Could be, but isn't [1]. There's a bunch of embedded GPL code in routers and various little bits of all kinds of systems that enable our current lifestyle, too.
I won't argue that for most (though not all) actual software intended to be sold, GPL probably isn't the best of ideas. But that doesn't prevent earning money while using GPL software.
[1] And certainly hasn't. I won't overlook the historical effect GPL'd code has had.
This means that there are categories of software where GPL does not really fit at all, games for example.