iPhone alarm clock auto-stops after 15 minutes

I am not an early riser, which is why face the following problem with the iPhone alarm clock.

It happens to me quite often, that the alarm does not wake me up in the first 15 minutes. In other words - I do not reach for it to stop it manually.

In this situation, I'd expect the alarm to ring continuously until I stop it (until the iPhone is sure that I am awake). BUT the alarm simply stops after 15 minutes and it rings no more, which makes me easily fall asleep again.

As far as I know, there is no way to change this setting (which surprises me).

I know that for most of the people, this is not a problem - they simply get up in less than 15 minutes, but as I said, this is not my case.

So I admit, I am complaining about my own laziness :-)

My question is - is there any reason for this?

Why does the alarm stop automatically after 15 minutes?