Pumps may be simple but I’ve heard experts in outdoor gear question whether filters are reliable. They can develop micro cracks and therefore invisible failure modes. Now, low failure rate plus low incidence of ineffective in the water multiply to low risk. But they’re not perfect. It’s also very easy to get a degree of cross-contamination.

Personally I mostly use iodine and boiling though I do have a pump. I’d consider getting a steripen though.