As for the original question unfortunately the way from an extension to postgres core is not too easy
and normally requires an extension to become popular and to be included in postgres distribution as a contrib module first.
Do you have a specific example of a patch being written for this feature and not being accepted into core simply due to lack of popularity? Generalizing here doesn't do anyone any favors - every patch and feature is unique.
I'll agree that somewhat marginal features are often passed on, especially if there is any non-trivial bike-shedding, but I do suspect that if someone took the time to write a patch for this and usher it through the commit process it would stand a good chance of being accepted. I don't recall a request for this feature recently (last couple of years) let alone someone putting forth an actual patch. That the core committers have not chosen to work on it is not in itself an indication of their opinion on whether the feature is worth adding.
There are no coding standards for extensions - there are for core. One cannot assume that a functioning extension can simply be dropped in.
David J.
