It’s all about convenience really. Why walk further than you have to? Even if it takes the hotel bus longer as it goes around the hotels, it doesn’t really matter as any time saved would either be spent waiting at the airport or waiting to leave the hotel for the airport. Plus let’s face it, London’s buses must be some of the least luggage friendly I’ve ever encountered with Metro newspaper holders taking up any space over the wheel arch and drivers that will start moving before you’ve even scanned your Apple Pay! That’s if the bus even stops as it might be full of airport staff getting to work and you’re at one of the last stops before the airport