Today it's hard to get any sunscreen which is not a complete sunblocker so people want to get _some_ sunlight just avoid some sunscreen altogether.
Yeah, I hardly see anything under SPF15, which lets 1/15th of the light in (6.7%). I'd be interested in using an SPF 5 or so (1/5th or 20% of sunlight gets in).
Those are usually sold as tanning lotions instead of sunscreens.