I think OP may be thinking something like finding a good fare in the MR forum or "good deals" threads, booking it immediately to lock in the fare, then having to enter a visa process that takes several days or weeks.

Denials are rare, but this does seem to leave the door open to getting stuck with an unusable ticket.

Also, I would assume that most people outside of FT aren't running around booking spare refundable tickets for this purpose. If you're taking a family of four somewhere that requires a visa, that could tie up quite a bit of credit during the process.