Eradication is really hard. If you just kill mosquitoes in a certain area, what’s gonna stop them from coming back? You’re just not gonna get all of them.
This way you introduce a mutation that can actually propagate through the gene pool, disabling the undesired trait for future generations. It’s also highly selective, so that you don’t accidentally get rid of other species or poison an area with pesticides.
Also living beings have no “purpose”. They fill an evolutionary niche and shape the ecological system around them. The piss off us, so we play a little god, but nature has no opinions or morals whatsoever.
We had a bright orange magic box that was connected to a beige windows 95 box that you were never allowed to turn off because nobody knew if it would survive a reboot and there was no software for the orange box for a more modern setup. Almost felt an like arcane ritual, typing in the command lines to get it to work.