The practice started when tubulars were made with silk (hence the term 'silks'). For these tires it was common practice to deflate them between rides to prevent stretching or deformation.

Modern tubulars or clincher are not prone to this (no silk) so there is absolutely no advantage whatsoever to deflating them between rides.

If you are going to put your bike in the trunk of your car and leave it in the sun for a while this may prevent the tube from bursting and damaging the tire but it has to be pretty darn hot to do so.