Board Game Arena

I really think BGA is a great site and I really want to thank all the developers who made this site for us.
But I'm often quite frustrated when it comes to expansions of some games. If the expansion was not released with the core game itself, we'd usually have to wait for a long time to see it coming.
Does anyone know why expansions are seldom updated, even when they do not seem to require a lot of efforts? Once again I truly appreciate every developer's hard work in building/maintaining BGA but I'm curious to find out why.

There are a variety of reasons.

It could be that BGA does not have the license for the expansion. Each expansion is its own legal entity, and just because they have the rights to the base game and some expansions doesn't mean they have the rights to all expansions.

The original developer may no longer be interested in that game. If the original developer doesn't want to add the expansion, it is difficult to find someone wanting to work on it. The developers are volunteers, after all.

The comment about "even when they do not seem to require a lot of efforts" is a difference between how the human brain works and how computers work. Imagine a resource-gathering game. An expansion of a single card that says "Every time a player gains any of resource X, they may gain one more of it" is very simple for a human to understand. For a computer, this means that now a section of code needs to be entered that checks if the expansion is being played with, if the player has that card, and generate the input if they want to use the option to get an extra one. Not only that, but that section of code needs to be inserted into the normal using a worker to get resources section, but also the market section, and the sections where players can give or steal resources to/from other players. The effort-to-fun ratio generally doesn't make it worth it.