I don't know if they offer larger packs for the push or walk-behind variants, but it's a matter of sizing the tool to the job more than electricity IMO.
It's a walk-behind variant, two 3Ah and two 5Ah batteries. Typically need both sets to finish the yard and if the grass is higher both sets aren't enough.
The yard the mower was purchased for has a lot of stuff in it to maneuver around so a riding mower wouldn't work well for the job.
Since every brand has to have their own battery system, the batteries being a large chunk of the price and everyone most likely already has a certain brands power tools + batteries in their household there isn't much of a choice.
It doesn't matter if I mow the lawn or cut wood with the chainsaw. I often have the impression there is not enough power both in force and duration for the yard work I'm doing, in particular if I'm doing tasks that I've used gas powered tools for in the past.
And it's not just power, the chainsaw for instance frequently seems to shut down cause it's overheating (independent of oil status) so you have to wait a bit before you can continue. What really pisses me off is when the tool shuts down to save power cause you had ~15 seconds of downtime.
Imho electric is nice and convenient for easy to medium yard work but to be honest I often find it's not quite there yet.