É claro que, para todas as coisas, Star Trek Memória Alfa tem as respostas.
Com relação aos suportes do transportador:
The transporters installed on Earth's NX-class starships featured one large circular pad that took up the entire platform. It was large enough to transport two to three people, provided they stood close together.
By the 23rd century, Federation transporter platforms featured multiple independent pads, typically six in a hexagonal configuration. One- and two-pad platforms were also available.
This became something of a standard layout for Federation transporters well into the next century. As an example, the platforms used on board Galaxy-class starships had the familiar six individual pads, with an over-sized pad (in the center of the platform) that could handle small cargo.
Por que eles caminham até a plataforma de transporte?
The outer hull of a starship incorporated a number of emitter pads for the transporter beam.
Pelo menos inicialmente eles criaram um feixe do bloco na sala de transporte, que viajaria através de um feixe criado a partir do casco. Não havia um emissor de feixe que apontasse para o interior do navio. Como resultado disso:
In the mid 2260s, beaming from a transporter pad to a location within the same vessel was a very risky proposition. The limitations of the technology at that time made it highly probable that any error would result in the subject rematerializing within a bulkhead, deck, or other structure.
Por fim, eles resolveram esses problemas técnicos:
By at least 2268, limitations in pattern buffer and targeting scanner technology had been sufficiently overcome that it was now possible to transport from one location directly to another without the need to re-materialize the subject in between. (TOS: "A Piece of the Action") In the 24th century, this operation was enabled and controlled by the site-to-site transport interlocks. (TNG: "Brothers")
Site-to-site transport holds the matter stream in the pattern buffer while the ACB was re-targeted. Afterward, the matter stream was redirected to the new location and normal re-materialization was carried out.
This technique could only be utilized when sufficient energy was available to the transporters; all normal transporter limitations would still apply.
Com base na última parte, provavelmente onde normalmente se espera economizar energia. Geralmente, é em situações de emergência que você vê pessoas usando transportes de site para site (como a enfermaria).