Just this week in Vantaa, Finland three 12-year-old girls piled onto one of those electric scooters you subscribe to with an app and proceeded to get run over by a car at a crossing, killing one of them
The app is supposed to have an age restriction but it's easy to bypass and you're not supposed to have more than one person riding on one, which people routinely ignore
I hate seeing kids and teens speeding around dangerously on those fucking things and then just leaving them laying around on high-traffic bike routes because they don't give a shit since they treat the scooters as completely disposable
Fucking awful bazinga-brained Silicon Valley-ass idea and business model. Actually, there are also bikes you can use with an app but curiously you don't see kids doing reckless shit with those, almost as if electric scooters were uniquely terrible 
So is there enough space on the sidewalk or bicycle path to park them without being obstructing?
Yes. They're doing this in designated parking areas, where people also park their bikes and the like. These are large zones with plenty of space and clear signage. Next to these zones I'll often see users of the rental e-scooters opt to throw them on the bicycle path or on the pedestrian path instead of walking/driving the last 5 meters to the spot put aside for their rental e-scooters.
Even if there was no space, I'd still complain about this however, since I do not see people do this with their own bikes and it happens to a much lesser extent with rental bikes. For whatever reason the system around rental e-scooters encourages irresponsible handling of the scooter.