Cann

In 6.0 and earlier versions, the maximum was only a few hundred brushes. (when PS 6 was released, having enough memory to load that many was rare)

The limits were increased for Photoshop 7 to allow up to 8000 brush presets.

We don’t allow infinite numbers to keep from overloading RAM, scratch space, etc. And it’s a good way to identify corrupt brush preset files.