Apparently because it isn't riding weather yet.
As long as the roads are not covered with snow, salt, slush, or sand...and you're not asking him to ride it more than 5-10 minutes, it can be ridden this time of year.
Worst case, if you have a vehicle with a trailer hitch, UHaul rents purpose-built motorcycle trailers for $15/day - tell him he's welcome to come along for the trip to get it to the shop and you'll provide the trailer. Honestly, he shouldn't have an issue with that, especially this time of year - the market for a 30 year old bike is slim as it is, and it's *incredibly* slim in January. If I was in his situation I'd bend over backwards to help make the sale.
If it passes, done deal, you hand over the cash and you own a bike. If not, well, you load it back in the trailer and bring it back to his place.
The actual safety is usually no more than 30-45 minutes so long as you have an appointment. Favor a real motorcycle shop vs a place like Canadian Tire or whatnot - again, this time of year you shouldn't have a problem getting same-day service for a safety at most shops, they're not exactly busy.
Really...if he stonewalls on the safety, I'd walk away - NOT worth the risk, safetied last year and new tires...or not.