Many of the elderly people who come by coach have to use taxis to get to this end of town, they just can't walk with luggage, so a drop off could be sensible, trouble is people aren't sensible, if a coach is willing to stop somewhere other than a designated stop it becomes a free for all with "just drop me here" or "just drop me there".
As for coaches parking overnight, they seem to be here, there and everywhere, a popular place, especially for foreign registered ones, is along the centre of Gloddaeth Street, longways on the car park.