Here's a good reason why you should not clean the fixtures around your porch lights--if you need a reason.
The lights attract all kinds of nocturnal flying insects. It's like the proverbial draw of a moth to a flame.
Spiders weave their webs on the light fixtures to trap their prey. If you remove the webs, you'll remove the insect smorgasbord.
Recently we saw an insect we'd never seen before on the light fixture: a praying mantis lying in wait, maybe to snare a moth or share the spider's bounty.
The porch light screams '"science project!" We remember our son's science projects in elementary school, including "Can a Plant Grow Upside Down?" and "How Fast Can a Yo-Yo Spin?" Somewhere the curious mind of a science student will look at the light on his or her front porch and ask: What insects are flying toward the night light and how many? How many predators are lying in wait? What do they eat? And, what roles do these lights and predators play in luring the insects to their death?
Meanwhile, the praying mantis has vanished. It's end of the season. Next year there will be many more praying mantids. One deposited an egg case beneath a table on the back porch. After they emerge and eat their brothers and sisters (no sibling love there!), one or more may hang out on the light fixture next year.