For the Lulz and Morale and possibly disrupting logistics. Last I heard the Russians are putting as many air defense systems around the Bridge as they can.

That's just a shitpost meme exploiting a popular Russian superstition. As for the landbridge, Russia is dependent on its railroad for logistics and the Melitopol area is an important transport hub, if that gets liberated or disrupted the value of the Kerch bridge becomes absolute.
The Ukrainian MOD just announced they're getting ATACMS, so maybe we get some Meme Magic™ by August.