Just to be contrary, I wear baggies far more often on a road bike than an MTB. That’s mainly because I take my kids places using a road bike – and I prefer not to go to Tumble Tots where I’m the only male over the age of 4 wearing lycra bike shorts!
Oh, but just to be even more contrary, I almost always wear baggies when riding the uni – for just messing around with some short liners, but for proper rides usually wearing lycra bibs underneath. Not really sure why, but I’ve got into the habit now, and it just feels right.