A copyleft license would prevent someone else, who does not hold copyright on Atom, from doing that.
This is called "open core" strategy and few companies use it correctly because there is so much incentive to focus development on the "pro" version and let the free/open one stagnate (or lack basic features).
I wish they had it released under a less restrictive license like BSD or MIT.
Of course, then when you don't get any contributions that only feeds the justification for focusing on the paid product, because clearly "the community doesn't care".
[1] mysql is the biggest and most obvious example, but it seems like a lot of tension built up over it and that's resulted in several forks existing now. Who presumably accept contributions without attribution to Oracle.
There is and it is called Google. It's a champion for Open Source and seems to use Open Source software almost exclusively across their entire organisation.
Of course there is Google, Amazon, Red Hat, SUSE, even IBM uses a lot of GPL software...
Plenty of businesses depend on FOSS desktop software, it makes them money. If I use Linux and tools like Blender, Vim, GCC, etc..., and I sell the resulting product, then I'm making money with FOSS, am I not?
So unless you make the effort to contribute back, they will have some issues to pay the rent.