If it happens once, then you are right. But when it happens lap after lap, then it's a problem and it should be punished. He carried more speed to that turn and gains time via this. He might loose bit of it at the exit, and maybe loose all of it or even loosing time in general in that turn by going wide, but this way he could protect himself against the attacking of RG in T4. So advantage is gained via blocking a potential overtaking maneuver, that's for sure.
Vettel did these when RG was right on his tail, but he could take T4 within the limits of the track when his position was safe and RG was outside of the "danger" zone.
You have a point, but sadly there are a good handful of corners in the calendar (like penultimum corner in Abu Dhabi) where it´s faster to go wide than to stay within the lines, and drivers go wide lap after lap (both in qualifying and race) there without consequences. So I think that if you´re making a "it should be like this" observation, then you have a point.
On the other hand, if you´re talking about stewards letting go something that is normally punished, that´s it, if you´re asking for a penalty for repeatedly going off the track limits by inches -and losing time in the proccess- then that is cynical to say the least in this context. That´s the nature of turf: if you go off you´ll lose a tenth or two instead of a second like before.
One more thing:
The regulations wouldn't need to change because intentionally leaving the track without justifiable reason is already banned, so it's not unreasonable for the stewards to say that, if you go off four times, on the fourth and any subsequent occasions, it's considered to be intentional.
Yes, the regulations would need to change to punish this. Because you´re only punished by gaining an advantage leaving the track. To get the scenario you´d like, it should be enough by going off -gaining or losing time- too many times. And in my view, that´s nonsense, as much as planting mines outside track limits.
I´m all for grass outside tracks and mistakes being punished, but now we have turf and rules are what they are. You only get heat if you gain an advantage. And it´s so monitored than a Vettel pole in Hungary was jeopardized because of going wide into last corner, that arrived to the stewards who deemed that after looking telemtery it became apparent he had lost time overall there.
That´s how the game goes now, it´s OK if you don´t like it, but let´s not act as if the game was another and someone got away with it.