When customers stay not because you're the best option, but because leaving would cost them more than putting up with you.
Oracle's flagship database has been the back end of large enterprises since the 1980s, and migrating off it is a multi-year, multi-million-dollar project that touches every dependent system. The customer doesn't love the product anymore, the customer cannot afford to leave it. The company collects double-digit-billion annual maintenance revenue because of exactly that asymmetry.