I received this email today:
Update: Freedom Convoy Trucker Funds The Canadian government has criminalized the receiving of funds from the Freedom Convoy 2022 campaign and now are trying to seize the funds to redistribute. In order to protect our Givers and the intended purposes of their gifts, funds not already transferred to the recipients from the 'Freedom Trucker Convoy' campaign will be refunded automatically, no refund requests necessary. Additional information will be posted shortly.
Why don't you go ahead and try to get people to mail cash up to Canada for the truckers. Doesn't even address the fact that they wouldn't even be able to use USD cash, so every person who is donating to the Canadian truckers would first need to convert some cash to Canadian money, then mail that money to a random person in Canada. Then that random person in Canada would have to open every single envelope from people and organize all of that cash, count it manually, etc.
Cash often isn't a realistic solution to many situations, despite the ability to typically give it to whomever without any specific tracking.