Those aren't substitutes. Tourists ride tourist buses to be taken on a guided tour, not as a means of getting from one place to another. Passenger buses and taxis don't provide that.

There may be an argument here about induced demand: more capacity results in more tourists until it gets too inconvenient at some higher level of visits, and similarly in reverse. But this suggests that removing capacity will result in bottlenecks due to traffic somewhere else. Things will get worse somehow until the word gets around and people reduce the number of trips they make.

It seems likely that 46 people will be unable to ride the subway or taxis and arrive at a single destination at once.

By blocking busses, onboarding and offboarding will not have the blocking behavior along with the other logistics of driving and parking large vehicles.

To computing terms, it's likely less efficient for the people on the bus (a large blocking operation) though more efficient for parallelized split groups of people and if not directly, then at least in diversity of groups of people.