When it answers a need that a sizeable percentage of your users have.
When it makes things easier for a sizeable percentage of your users.
When it can be done at a reasonable cost.
When someone with significant clout specifically hires you to. - In enterprise software it sometimes makes sense to build things to order for a specific client, even if just as one-off project.
When it saves you money behind the scenes.
And, to a certain extent, when you can rapidly prototype it and don't know what will happen - you can sometimes spin it off into a separate product if you're large enough.
Note that need and easier are not things that the users necessarily know themselves.
When it makes things easier for a sizeable percentage of your users.
When it can be done at a reasonable cost.
When someone with significant clout specifically hires you to. - In enterprise software it sometimes makes sense to build things to order for a specific client, even if just as one-off project.
When it saves you money behind the scenes.
And, to a certain extent, when you can rapidly prototype it and don't know what will happen - you can sometimes spin it off into a separate product if you're large enough.
Note that need and easier are not things that the users necessarily know themselves.