When use mast strobe light?
Manufacturers sell Strobe Lights because we will buy them. They are expensive because they cost a lot to make.
We buy them because we think (rightfully) that we may want the brightest, most obvious signal possible, in extreme situations - rules be dammed.
See the COLREGS (Rules 20, 21, & 36)
- Rule 36
Signals to Attract Attention
If necessary to attract the attention of another vessel, any vessel may make light or sound signals that cannot be mistaken for any signal authorized elsewhere in these Rules, or may direct the beam of her searchlight in the direction of the danger, in such a way as not to embarrass any vessel. Any light to attract the attention of another vessel shall be such that it cannot be mistaken for any aid to navigation. For the purpose of this Rule the use of high intensity intermittent or revolving lights, such as strobe lights, shall be avoided.