The main reason is that you get more damage out of CO than PPP and that’s why it is preferred. Statusing enemies is a natural and common occurrence in Warframe missions. In order for PPP to be better most of the time it would take an environment where status procs are less frequent to the point that the flat PPP bonus is higher more often than the CO bonuses and this simply isn’t the case unless you can craft this theoretical environment (by playing solo without a companion and also ensuring that you have very low status chance on your weaponry). Or you could just play CO which is fine on its own but scales up (hard if you lean into it with priming).
In Warframe, flat bonuses are fine until you reach harder content where your build will need to ramp up to keep up.
While not exactly what you might be looking for:
There are tenet melees that pause combo when you sheathe them. You would still be relying on combo but could put it away and save the multiplier for when you’d like to engage in melee.
Innodem is good as a combo weapon or heavy attack weapon and would be my suggestion. With a heavy build, corrupt charge, and covert lethality you can always activate the incarnon mode (with the proper evolution) via heavy attack without starting a combo in order to get the running speed bonuses and additionally the forced slash procs on the heavy dagger attacks will make mincemeat of SP enemies (since slash DOT ignores armor.
The Vastilok can get a 12x combo within 1 or 2 regular attacks (double shot from High Noon stance) using the Quickening mod while applying slash and stripping armor extremely fast. So while it does rely on 12x combo the combo is basically free. This works well for frames that can’t deal with armor and don’t want to play Unairu.
That’s my 2 cents.
Good luck Tenno.