Down here in NZ my city used to have these too! Apparently it was the last commercial trolleybus network in Oceania. But as a mostly suburban kind of city environment (not quite American suburbia but still low density), their utility definitely was quite limited by the predefined routes. Eventually more and more routes weren’t even using them. But they were still servicing the old main road high frequency routes, so they were still very useful in those instances. Much better than the diesel buses, too, which were so loud you could hear them coming from several stops away! Eventually they phased the trolleys out in 2017, citing all the usual rubbish like maintenance costs and such. But we hadn’t yet electrified our bus fleet, so for a while we had to borrow a bunch more diesel buses. Still on the road to having a fully electric fleet, and I imagine it will be a good while yet before that happens.