Because someone chooses not to play fast it doesnt follow that they are not capable of it .
[imo]some dance tunes[slides]which often have fewer notes,work quite well played fast.
Johnny O leary , in an interview, blamed the dancers,I am not sure it is as simple as that,many people who play in sessions,have never played for dancing.,yet play reels so fast that dancers,that imo are too fast for enjoyable dancing.
funnily enough, I have been accused of playing reels too fast,although I generally play them between 200 and 210[or 100 to 105],which would be considered on the slow side .
so I am talking of reels played at speeds above about 225 .
of course many dancers play to recordings these days,and the recordings can be artificially speeded up after the recording[without altering the pitch].