why are they scumbags? Because their business model doesn't align with your use of their software?
If you are a professional, you make back their monthly fee from a small percent of your profits from the first job of a month. I just did a $500 photo job. $480 in the bank after paying my $20/mo LR 1 TB plan. I had to share a web album to a client with 2,000 photos. They used LR web client to choose the photos they wanted me to retouch/edit. Maybe I'm off but I don't think Pixelmator offers anything similar to this.
I'm really happy there are cheaper (or free) alternatives for enthusiasts or part time professionals that don't need everything Adobe offers or who can't stomach the monthly fee.