Tin can man, my (pretty darn educated) guess is that among those who can afford the Grandma's weekend experience ($300/night, three night minimum unless they had chosen to stay in the college dorms), there aren't too many for whom that $100 is make or break right now. Sure, there are some, and I wouldn't be surprised if Grandma's were trying to set up a way to get refunds to people who truly need them, because they are good people. But most of the registrants will be okay without that $100.
In contrast, if the race were to furlough the staff, that's nine people completely out of work, and a race that thousands of people love gone. And for what? If there are nine employees making an average of $70,000/year and they were furloughed for a full year, that's $630,000.
With 18,500 racers, $630,000 provides only $34 per person - not even half of a full refund. So now you're saying you want to destroy a historic race, beloved by thousands of people, and put its employees out of work, all so that a group of mostly affluent registrants can get back $34/person. And, note - the staff have already been paid for most of this year's work. Grandma's will have been counting on the revenue from the 2020 race to make payroll for these next few months, until October when the 2021 fees start coming in. If you refund the 2020 money now, you're probably not just stopping payroll - you probably have to ask the employees to give back some of what they have already been paid.
Again, this is selfishness. Yes, other races can offer refunds because they are bigger. They are in larger markets, which makes their corporate sponsorships much more lucrative. You think Grandma's gets as much from Wells Fargo for advertising in Duluth as the Chicago Marathon gets from Bank of America for advertising in Chicago? Nope. They probably get 1/10th as much, at best. Other races can carry bigger year to year budgets because their fields are big enough to allow that. Grandma's can't, because there's literally no more hotel space in town.
Grandma's is not like other races. It's a big race in a small town. That limits its sponsorship revenue and its ability to carry a deficit and overcome one once it is incurred.
If you think it's worth having Grandma's die so you can have a few more dollars, fine. Those of us who cherish this race don't agree, and hope that it in the future you will look elsewhere for your racing.