It may have BECOME “common practice”, but it is by no means acceptable just because of one’s position...
No person should be above the law...NONE.
The people who write the laws usually write in exceptions, for themselves, for other government officials, etc. That way, they can say that are acting within the law, even though the law is written so that it doesn't apply to them. If there is an oversight, the courts write in the exception for them.
It is a matter of efficiency and expedience that higher authorities are accorded exceptions in matters such as this. I take no offense whatsoever if my mayor must use a quicker process to get from one place to another. There are other displays of arrogance and abuse from high officials that are worth braying about, but simply attempting to be expeditious with official business is not one of them.