So if I apply your argument to another form of transport, we should only be able to rent cars, not privately own them?
OK, not a completely fair comparison as they have a number plates to track them more easily. But if the police stop an e-scooter what's to stop them checking you have a valid licence regardless of whether it's rented or owned?
I accept that it's a trial and will hopefully lead to a complete change. I don't own an e-scooter but have some friends that commute to work on them.
I do also think they should change the speed limit of e-bikes to match North America, but that's another topic.
By starting off this way, there can be some control, and we can help reduce the possibility that hobbyists with modified/homebrew scooters are not flying around on 40mph scooters with tiny wheels on the roads and pavements without recourse. The car comparison, as you say, is clearly not the same.
Just for a start the barrier to legal usage of licensed travel methods is much greater with a car/motorcycle than e-bikes and scooters, not to mention they are proven, regulated, and relatively safe.
Lets say that we allowed e-scooters unregulated tomorrow... We could have young teens and even children with no road sense, no helmets, doing 30+mph with tiny wheels unsuitable for such speeds, without the required infrastructure. If you are pro-e-scooter, this is a great baby step to making it a viable industry/travel method in the UK. Its unlikely to be rolled back now it started, and this is the beginning for wider adoption.
Scooterists should be very happy!