That's the point though. If you accumulate 2x 10 second penalties nothing stops you from staying on track and just getting time added to your race time, while you slow everyone down to advantage your team mate.
If you get 2x 10s time penalties and have not yet served one, giving a drive through solves both of those problems because it HAS to be served (unless it's not handed down until the last couple of laps or after the race, obvs.)
I don't hate the idea of converting two 10 second penalties to a drive through if you haven't served the first.
What I was arguing against was more the idea of generally increasing the penalties (again) so drive throughs are given more readily for stuff like overtaking off track. An argument you see a lot these days, especially on Reddit.