How necessary are barrel adjusters?
I have to say this first: riding a bike when part of the brake system is not assembled as it is supposed to be is potentially dangerous.

The brakes may seem to work fine but if the housing or adjusters are not seated properly they may come adrift and leave you with a non functioning brake. 

Brake and shifter barrel adjusters are necessary to fine tune caliper engagement and shift indexing. I do not recommend removing them as one day you will wish they were there.

Backing a barrel adjuster all the way out will not strip the threads as there is no thread engagement therefore no damage to the threads. They can be a pain to get back in though. If you disengage the cable at the caliper temporarily so there is no tension in the cable it may be easier to screw them back in. Alternatively have a local bike repair shop sort it out.

You may also want to check out some online resources on proper brake adjustment. Park tool has a particularly good set of videos on their YouTube channel.