Road or MTB racing – padded lycra only as otherwise I get too hot and none of the reasons below come into the equation.
For more serious/technical riding I like padded lycra with baggies/overshorts as they:
1. Offer more protection if you come off and stop your lycra getting holed.
2. Offer more protection from mud and water (esp if waterproof) so I don’t get as wet and uncomfortable on longer rides and also stops the pad being destroyed by grit, etc. They also stop brambles, nettles, etc from destroying my legs as much. Help keep me warmer in the cold too.
3. Hold a map and compass where they are readily to hand without getting in the way.
4. Reduce the rubbing that can occur on rougher rides. Smooth terrain is fine in lycra but baggies give an extra layer of movement that I find reduces chafing over choppier ground.
Please note that these are MY opinions of why I wear them in response to the OP. You don’t have to agree but neither do you need to persecute or disparage me or others for our choices that, at the end of the day, do not affect you in any way, shape of form. Both sides need to get over themselves.