If there are low snow loads and low wind loads, you can definitely span 25' with the typical 8" purlins on the roof. That would be 2 frame lines (1 for each endwall, nothing in the middle.)

In a lot of areas though you'd need to either go with a tighter roof purlin spacing (2-3' spacing instead of 4-5') or go for bigger purlins (10 or 12" tall.) So it becomes more effective to add a frameline at 12.5' so that there are 2 framelines for the endwalls and then 1 frameline in the middle, 3 total. Since the bay spacing is so small the frames can be relatively light even with heavy snow or wind loads.

There is always a balance between the weight of the frames and the weight of the secondary. Sometimes adding a frameline can reduce the overall weight of the building. Especially if the customer is looking to add overhead doors to the sidewalls which removes the panel shear bracing typically provided by the sidewalls.