Too many opinions on this thread and hardly any facts.
1) This is a common occurrence all over the world where people are impoverished. We fly to many airports where the taxiways are monitored and some where we are even escorted to the runway to prevent would-be stowaways.
2) How desperate is the person who tries this? Apparently willing to die trying.
3) Those who "succeed" are the ones who go undetected. They do end up dying.
4) If airliners turned back for every "maybe", there would be a whole lot of turnbacks all over the world, and most of them unfounded.
5) It's IMPOSSIBLE to see from the cockpit windows if someone is stowing away in the wheel wells.
6) If the flight crew and airport authorities had POSITIVE confirmation that a stowaway had succeeded in gaining access to the airplane, they would definitely have returned to the field.
Don't stand on the sidelines and speculate. If you want to talk sh#t, at least know your sh#t.