Actually, at higher levels of play, they can very well spam just as much if you let them, lolz. Don't believe me? Play some sets against Bones and Zanguzen.
It's just that their opponents are probably better at getting around it, so it doesn't seem like they're camping.
WDing OoS between lasers is useful. Once you get close enough, Falco won't be able to freely shoot lasers anymore because at a certain distance, even being hit by the laser won't make it safe for him. If you can make it onto a platform at a safe distance, you can try to drop a missile between the lasers. The lasers are transcendent, so you'll immediately force him to respect your missile as an option. Once you get in, try to stay in but don't try to force anything if he gets away. Shooting uncharged shots can also force him to respect your options.
Edit: As 343 said, try to use platforms to your advantage. If you are standing on a plat fairly close to Falco (say you are on the right edge of the left plat and Falco is in the middle of the stage), he should stop lasering and respect your ability to come down with nair. If he doesn't.....then hit him.
Once you start outsmarting their laser options, they might start running away to platforms. At this point, the MU can become really annoying.