They can ship their own product and give it away till you go bust, then start charging for it; and use secret APIs you can’t see; and they can break the published APIs you use. All of these things have historically been done by platform vendors.
Rails Long Term Support
Rails LTS provides security patches for old versions of Ruby on Rails (2.3, 3.2, 4.2 and 5.2)
Prevents you from data breaches and liability risks