Double-deckers are primarily for commuter transport but open-top models are used as sight-seeing buses for tourists. William Gladstone, speaking of London's double-deck horse-drawn omnibuses, once observed that "...the best way to see London is from the top of a bus".

Why are there double decker buses in London?

The main reason for their continued popularity was because the single-level buses simply couldn't hold enough people, and the longer accordion version couldn't handle London's narrow streets. People also liked the viewing capacity and having open tops.

Why does America not have double decker buses?

The US has a very strict Buy America policy for governmental vehicles (which includes transit buses), so transit agencies could not purchase double decker buses even if they wanted to.