I'm fine with the mechanic and use it quite often. I mean, when you ace the enemy team, you give them access to the shop and allow them to come back even stronger. A tower suicide (or a few) just maintains the advantage you gained by winning the fight in the first place. The team that won the fight should be the stronger team, that is how this game works.
One of the reasons a team can get stronger and push is through suicides. Think about it, if no one suicides, you will end up with a constant back and forth. Win a team fight, now you have low health and less items, and lose to the other team. Now the other team has less items and low health, and will then lose to balance it out. Rinse and repeat.
It adds another element to the game. Think what you want, but I'm much more enthusiastic about a tower suicide, as opposed to waiting around on 200 health to get killed. No one likes being useless.