Rubbish: they can be successful because not everyone wants to buy a scooter. Also commenter still probably uses Bird, for example one way trips or when it is just more convenient.
I've also rented a couple Lyft scooters out of convenience, as you said. They certainly feel worse, now that I'm spoiled, but the convenience of just dropping them off is a huge win.
running errands
You stop for your first errand, come back outside afterward, and bam! someone else took it. What if there are no others nearby?