I have Ego's bicycle handle brush cutter, think a weed whacker on steroids with a metal blade.

That think does some serious work. I've cleared acres of overgrown mess with it. 2 6aH batteries will outlast me (~2 hours) before I need a break and the fast charger tops one up in maybe 30 minutes.

Lawn mowers are really where batteries fall apart. They go through a charge extremely fast, especially if the grass is even moderately overgrown. Most mowers are meant to be finish mowers where you aren't taking off much grass at all, say 1/4" up to maybe 1". Electric mowers really demand that or you'll run out of juice very fast.

It’s not practical for all crews at present due to costs, but as EVs become more entrenched, the problem will solve itself. You keep an extra set or two of batteries that the truck charges and you swap as needed, not that different from having to stop to refill on gas.

Energy density of batteries is improving too, so the amount of time between swaps will be increasing.

My cows do a pretty good job, but I've always heard that the way llamas eat works extremely well for grass management. Something about biting off the grass rather than pulling/tearing it.

I have 40V electric lawn mower. It takes nearly the full charge on two batteries to cut my average suburban-sized lawn. Sometimes I can't even complete it on that depending how tall the grass is. Add in edge trimming and blowing away the clippings and then multiply that by a number of lawns or larger properties and I think you would need dozens of batteries.

BTW "more convenient and cheaper" are strong arguments when you're in a competitive business. Lawn services are usually just a guy with a truck hustling for customers. The more lawns you can cut the more money you make. Anything that causes downtime such as running out of charged batteries is going to be a large negative.