Well i feel that if this option could be easily implemented i see no reason why it shouldn't be implemented. It wouldn't influence the game play in any bad way since the option would only activate when a shiny appears and it would certainly solve the headache from lots of people that play this game a a lot. In my case and in cases of several other people i know, where we would hunt for a pokemon for hours or even days, we all had to deal with the headache of a lost shiny.
For someone to say "pay more attention to the game", I don't think its possible to give the game 100% of your attention at all times and also people play this game to have fun, sometimes doing several things at once.