I've always thought of lube as something for handjobs or anal, or for if your vagina isn't wet enough--as a way to compensate for dryness, in one way or another. I figured, my pussy gets plenty wet, so for regular PIV sex or fingering, there's no need for lube.
Well, there's no need, but boy does it make a difference. Lube doesn't just bridge the gap between "ow" and "yum," but between "yum" and "OH YES OH GOD OH FUCK." You can think your sex is totally soaking wet and working fine, then add some lube and realize what you've been missing. I don't even fully understand it, but I'm coming to accept that it's true. Wet sex is good, but lubey wet sex is GREAT.