Because it was required.
It was part of the agreement that you signed, with your own energy imprint, when you asked to take part in this incredible experiment/adventure/school/game that is commonly referred to as the Human Time-Space Illusion or HTSI. That agreement said, in effect:
For the purposes of this journey/game/experience/whatever you want to call it, I agree that this time-space illusion is absolutely real and that for the duration of my visit to Planet Earth and its vicinity I will be bound by the constructs, limitations and illusions that are currently agreed to by the societies that have developed within this illusion. Furthermore, I understand and agree that, for my safety and that of others, I will not be able to leave this illusion until I have discovered the key hidden deep within myself. I may drop the human body, but I will always be drawn back into a new one until I find that key.
You might say, “I never signed anything like that!”
Well, the truth is that most angels were so excited when they discovered this place and saw the results on the ones who had been through this HTSI experience that they never bothered to read the agreement, but it bound them anyway. A few even thought they were clever and tricked their way past the gate without signing, and those tended to create a lot of drama when they got here. But sooner or later they found that they too were bound by the agreement, and were therefor no better than anyone else.
And now, dear friend, you are beginning to wake up.