It's called netiquette (or netiquete, not sure ATM, and spell check doesn't appear to be working).
Mostly, because the real answer to: "when is it done?" is: "When it's done.".
And modders tend to become a bit grumpy when it keeps having to be said.
There is another aspect to it when it comes to bridges.
The bridge modders we have are currently the only bridge modders there are.
So, an additional feeling would be: "Why do you care when it's done? We can stop right now and it will never be done. Be glad that we are doing this." but only after answering it after the gazillioned time.
To be the only ones that can do it puts a bit of extra pressure on your shoulders.