Its true that you can be ordered by the court to decrypt drives. Then there is a documented point-in-time when the state received read/write access to your drives, and also, presumably the drives are already in custody etc.

I think the highest risk of evidence being planted would occur during the search and seizure process, so encryption would help you there. And it also prevents informants from doing it and then selling you out for their own benefit. And it prevents thieves from looking through your files if your bag gets snatched.

Overall I think disk encryption provides some great benefits.

EDIT: although you have to be more careful about data loss, for example: https://www.gwern.net/Notes#november-2016-data-loss-postmort...