I suspect, since you refer to this being a multi-file database, that you may be dealing with an older solution that was converted from the pre-version 7 days. In earlier releases, you couldn't prohibit field entry using layout options. Hence, some developers resorted to using a calculation field that simply echoed a value out to prevent users from altering it.
Nowadays, such techniques are obsolete. And you're right; they generally serve no good purpose and contribute to database overhead. The only exceptions are certain, somewhat obscure, instances where you need to echo a field in table A because the value in table B needs to be reflected in related table C (in a portal, for example).
Thanks Mike. I'm almost sure this was a pre-7 database originally, so what you say makes perfect sense.
A little more info, in case it helps somebody: the related fields in question are global container fields that hold icons used in buttons in many of the layouts. When I take a copy of the database with all those fields deleted, I get a huge increase in remote performance. I'm next going to try a version with the fields still there but the method #2s converted to #1s. I suspect I'll lose most of the performance gain, but I want to give it a shot. Probably need to find simpler icons or go with text-only buttons (maybe a symbol font), to maintain the big performance jump...