Do I actually need gaiters for day hiking?

For dry, well-maintained trails, no. Reviewers across r/UKhiking and r/PacificCrestTrail openly admit gaiters are skippable in many conditions, with some PCT hikers saying they stopped bothering. The case for gaiters gets stronger in three scenarios surfaced repeatedly in mainstream expert reviews: snow and shoulder-season slush, scree and loose talus that flicks pebbles into your shoes, and brushy off-trail terrain where pant cuffs get shredded. Trail runners on technical singletrack also report fewer foot stops to dump debris.