They are renting out the hardware for minecraft servers, not the software. The software is free for anyone to use, whereas the hardware costs time and money to maintain on top of the initial investment. If you think they are scams, your wrong.
If you want to go through the process of setting up port forwarding, a dedicated server with 24/7 uptime, basic ddos protection, automatic backups, and go through the process of maintaining it, be my guest. If you don't want to, or far more likely can't, you can rent a server or just play on any available ones with your friends.
