I think it's a mix of things. Some folks genuinely prefer the tactile experience of holding a hymnal - there's something about the physical book that makes people feel more connected to the practice, plus older congregations often have members who find projected lyrics distracting or hard to read depending on eyesight issues.
It's also way cheaper to maintain books you already own versus investing in projector systems and dealing with technical glitches (I've seen plenty of those fail mid-service, trust me).
A lot of churches stick with what works for their community rather than chasing what the megachurch down the road is doing - kind of like how I still prefer my old field guides to birding apps even though everyone tells me I'm being stubborn about it.