Because it is Anime.
Anime physics is a fanon term used to describe all the unusual, impossible, and sometimes absurd moments in the anime where real-world physics do not seem to apply.
Example :
In Sweet Baby James, Jessie picks up May's Munchlax and puts it in a bag, despite it weighing over 220 lbs (100 kg).On another note of this, in Off the Unbeaten Path, Max was able to carry it on his back despite Munchlax weighing around four times as much as Max.
--http://bulbapedia.bulbagarden.net/wiki/Anime_physics
It's for making cartoon fun for children only, not to make actual meaning to others(elders, etc)