Lightning is vertical scaling.

Drivechain is horizontal scaling.

Allows for more experimentation and free market competition for scaling and features.

Its trustless in the sense that the only trust you are dependent on is that bitcoin miners are profit seeking and will merge mine sidechain blocks for extra revenue.

Its an opt in system so only those who wish to use side chains will use them. If you are not interested then just continue to use lightning and mainchain. 🤙🏻