You can, but it's easier to evade fares. The driver can enforce fares better at the door near them.
My local transit agency just stopped allowing rear door boarding, and that was one of the main reasons: https://waypointblog.com/capmetro-is-ending-rear-door-boardi...
maybe i dont understand how articulated bus makes boarding faster. If anything it makes it slower compared to double decker .
The goal of public transportation is to move people fast around the city. Not to have the driver sell the tickets, that’s what the ticket machine is for (both on stations and on board). Anybody using public transportation daily probably has a monthly ticket anyway. And not to provide tourist information.
People want to get to work on time after all. Entering and leaving the tram or bus through all door is a simple way to improve public transports reliability.