Ask HN: Why do seemingly minor features take companies so long to implement?

For example, Tinder just came out with an update today that allows users to limit their matching results within an age range, a feature that people have been asking for since the beginning. I dont understand how a feature like this couldn't be implemented in under a week, with a solid team. Why do updates like this / new features that don't sound very complicated to a user, take months to implement? Am I missing something about the development process?

thanks. those points are great, and I get how those can be factors in a major / delayed / completely new update for a company like dropbox ( because security holes cannot happen whatsoever (3), it already makes money off of its customers, so it should consider (1) and (7), and that it might have other features in the line (2) because they have several products / features already ).

But in tinder's case, the addition of age preferences in matches is similar to their already-existing gender & location search for a couple reasons... 1) they already check a potential match's gender (and location) against the gender preference you chose, so while they're there, how much harder is to check another attribute of that match? his/her age, 2) they already have the matching preferences / UI setup (yes, decisions still have to be made about where to put a slider, but it shouldn't look too different from the distance preference slider, and it's not such a new feature that it would be confusing to the user), and 3) since they don't currently make money off their user base, tinder's main value is derived from # users, # active users, etc. There could be an argument to be made about making it a possible premium feature, but bringing in more users / giving users what they want / making them happy should be the focus.

I guess when it comes down to it, I just don't understand how the development process of similar feature could take so long.