Short Monotype Descenders

I vaguely understand that Monotype had limitations on the length on descenders. Here's an ad from Lanston Monotype advertising fonts with longer 'traditional' length descenders. What exactly stopped them from having 'longer' descenders? 

Are any of those fonts affected with short descenders still around in digital form and still with the short descenders?
Did typographic standards and thusly our reading tastes/habits change because of this limitation?