technology - In Star Trek - What's the Point of the Transporter Room?

I hope this isn't a silly question but I've been watching TNG and this bothers me.

The transporter 'pad' area is relatively small. As a guess, maybe 12 people can fit on it. But the vast majority of times it's being used by 2-3 people.

However, the transporter is able to beam people from anywhere on the ship to anywhere (within some distance I presume). It's fairly common for them to perform a transport directly to the bridge.

So, why is there an actual room?

If a three man away team is to beam down to the surface of a planet - why do they have to walk all the way to the transporter room, then stand on the pad to get down there? Why not simply beam them from where they are, to the surface. The ship's computer is able to locate anyone on board.

Answer

Of course for all things Star Trek Memory Alpha has the answers.

Regarding transporter pads:

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.

Why make them walk to the transporter pad?

The outer hull of a starship incorporated a number of emitter pads for the transporter beam.

At least initially they created a beam from the pad in the transporter room, which would then travel through a beam created from the hull. There wasn't a beam emitter that pointed towards the inside of the ship. As a result of this:

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.

Eventually they resolved these technical issues:

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.

Based on the last part they probably where expected to normally conserve energy. It is typically in emergency situations that you see people using site-to-site transports (such as to sick bay).