well it doesnt 'have' to if your being pedantic, but it is advised, otherwise u are putting a large strain on your calves as they are not allowed to rest.
take moving into minimalist shoes slowly it will be worth it in the end. I made the change 9 months ago and i feel far better than when i ran in shoes. I run in luna sandals and vibram bilikas i find both are great. I wear injinji socks with both, great socks that wear well and dont cost the earth. I wear my vibrams and luna's all the time for running, tarmac and trail.