It's not like your giving every single person on the server fly mod. All your doing is giving everyone the ability to use it, if they so choose. Which as it appears, would actually be a small population. However, there's still a good number of people who would like access to it. And there are a number of reasons why one would want access to it.
It actually enhances touring the server imo. I'd rather see those nice mountains far off in the distance, and be able to get over to them quickly, and check them out, instead of having to spend ages getting over there with normal fly. Or fly fast overhead a city and take it in at multiple angles. Tbh its kinda hard to describe, but if you actually used flymod to tour the server, you can tell its a much different, and better, experience than you get with normal fly.
Its also extremely helpful for people trying to take screenshots of large areas. It allows you to get to chunks that have deloaded faster, and explore multiple angles, and then get to a good angle to take a picture before anything else deloads.
And also like dags said, its rather useful for building, at times, as well.
But what i really don't understand is why people seem to be acting like its some ridiculous, and dramatic, demand; when its really just a simple request. Its not something we need, no. But its something that quite a few people would like to have. And i dont see why a simple luxury should be restricted, unless of course there is good reason.
Now, if there is a legitimate reason for us not to have access to it (such as lag, or like iru said possibly downloading of the map) then ok, that's fine. But then maybe artists could be trusted enough with it? A smaller pool of users, and for the most part "trusted" users? I dont know, but its a suggestion.