As far as I am concerned, squad numbers are better than numbers issued at the start of every game. Some players cannot always be immedialtely identified from the back and are recognised from their numbers.
I think that was one of the reasons persistent numbering was introduced. More and more games were being broadcast on TV, stadiums got bigger and better, screens were installed and let's not forget - the rise in importance of club merchandise.
With the old system, I think it was George Best who because of versatility had worn most numbers from 2-11, mostly of course 7 or 11.