Segregated services for commuters are great, but catching a bus to shop/recreation/restaurants is miserable and restrictive.
As as aside, developing mass transit always has the problem of being at the whim of the next political goal (subsidised bus routes especially). Roads are physical easy to understand, so less subject to political vs.
???
Yes, roads require less 'active upkeep', an austerity government might stop funding transit but they will not close roads. However, this is more of a feature of the supposed 'independence' of car transport, not 'easy to understand'.
In addition, defunding transit would be a lot harder and weirder if it is in a form that requires actual infrastructure (metro, train, tram) rather than some stops and a schedule (bus). That's one potential reason to trust bus transit projects less.
Do keep in mind that roads aren't free after construction either; they typically require pretty significant upkeep (especially things like repaving, but also e.g. traffic signals).
Roads are public in a way that introducing a toll on an existing road is not politically viable, and maintenance issues are easier to spot.
> The double decker buses are beloved.
You haven't the slightest idea of what you are talking about. See "little to no experience with daily reliance on buses for urban transportation".
Bus rapid transit can actually be really nice. You know that rock stars and politicians practically live on buses while they do traveling events? Of course a BRT isn't going to be that private luxury, but even a middle quality charter bus that makes limited stops is pretty darn good. Having dedicated lanes removed the worst part of buses compared to trains.
I used to daily take the AC Transit transbay buses from the East Bay to San Francisco, which are double-decker Greyhounds and have comfortable reclining seating with tables and wifi. The single entrance/exit is a benefit, because it only runs commuter hours and so in the morning it only picks up in the East Bay and drops off in SF. It allows enforcement of fares too. It's a higher fare, but that also attracts a commuter clientele. The main problem with it is that it is too popular and gets crowded, and you're SOL if all the buses are already full at your stop. But that if the flaw is that it is too popular, that's the best and easiest problem to have. Sometimes a regular AC Transit bus would show up and we would all groan and curse.