The problem is that too much of a Sorcerer's abilities are based on spending spell points. Sure, you can create bonus spell slots, but often it's too expensive to do so unless you want to blow your entire daily allotment on one slot and not use any of your other spell point-dependent abilities (this is especially true if a 5th level character wanted to create a 5th level slot, since that costs more points than they have per day so they'd need to sacrifice a 2nd or 3rd level slot or two 1st level slots for extra points). Sorcerers also get skunked on number of spells known: at 20th level they know 15 spells, a number that's comparable to the number known by Arcane Trickster Rogues and Eldritch Knight Fighters, versus the 44 a Wizard would learn just from leveling (25 of which would be prepped). Plus Wizards have Arcane Recovery, which means they can cast substantially more spells per day than Sorcerers (in addition to having a dramatically larger spell list).
Sorcerers are much less flexible than Wizards.