I do not directly qualify to answer this but i follow aviation industry very closely, hence taking an attempt.

1. Body clock- the natural body clock gets drastically disturbed. Long flights need the crew to be attentive for long durations and aslo the altitude and speed messes up the biological clock.
2. Whiny travellers- let’s face it. We all have seen some really angry and whiny customers complaining all the time.
3. Might not be able to attend family in sudden emergencies.
4. The pay is not the most handsome in private indian budget carriers.
5. You need to be energetic and have a smile on your face ALL THE TIME.

Although these problems exist, it is probably the best job for those who want to travel the world.