That has not been my experience. Wizard was designed to be better at some things like number of spells. I never thought they needed this ruling, even if you warned them up front. Maybe if you had a training/level for all the PCs I can see this rolled into their training.
Training is off the bat. Players (12 of them) voted against that one at the beginning of 5ed.
The reasons that wizards are so popular in my games (go figures, I want warlocks and sorcerers
)
1) Ritualist. They do not need to have a spell in memory to cast it as a ritual. This makes spells such as detect magic and identify almost ridicule. As ritual, they do not need a spell slot to be used.
2) Spell versatility. The versatility the wizard enjoys as an arcane caster is unparalleled. The players consider the other casters as one trick pony (a bit of an exaggeration I know, but I say that to illustrate my players' mindset about the other casters). It is the versatility of spell choice that makes wizards so desirable.
3) Even without free spells they would make wizards! I tried it and they were still making wizards. Players are pooling their resources to buy spell for the wizards. Wizard is the character class most chosen for level dips... right before the warlocks, rogues and the fighters. This goes against everything I have seen at other gaming tables and on this forum (Paladin/warlock, or paladin/sorcer? Never saw them in my games... well, once but you get what I mean...)
In fact, even with this "limitation", the players are rolling dice to see who'll get to make a wizard when we create a group. The new group was created after a TPK and this is the first time, this player gets to play one. Do you see my problem? I want to see warlocks and sorcerers and yet, wizards dominate. Am I the only one????????