As long as they are not little round, fat, mites that want to stick to your snake, I wouldnt worry too much. Its kinda like how you get gnats everywhere when you have house plants. The grubs are just in the soil. Lots of reptile substrates come complete with bugs of some sort. There is no way they can prevent it at the packaging factory without making it dangerous to your reptiles. IE, using chemicals etc..

BUT, they do sell some natural mite sprays for reptiles that you can use on the bedding to try to get rid of the little buggers. It usually works since mites, fleas and ticks are much more resiliant, so anything that kills them will kill just about any other bug or at least chase it away.

I recently had to go through my entire pantry because I kept finding grain bugs on the floor in my kitchen. Turns out a bag of flour had them and I had to throw away everything grain related that I had. Bugs are everywhere. You just dont want the ones that feast on your animals to be in your house. Or the ones that provide that extra nutty protein when they get into your flour lol! (joe, you better not even touch this!)