Many places build dedicated bus lanes, and a few places build roads specifically dedicated to buses, like the Queensland Busway system

https://en.wikipedia.org/wiki/Busways_in_Brisbane

That’s cool but one counterexample does not negate the general trend. Most places have few dedicated bus lanes. Most cities have approximately zero dedicated bus roads.

Even the cited system seems to be limited and exists to connect with trains as well as buses that use normal streets. Wikipedia says that they chose buses for this expansion instead of trains specifically because there was already a strong bus system, which uses the same city streets as cars and trucks.