Oh, so not free, either in terms of money spent or time spent to send that thing off. If you're like most working people, time and money are both at a premium.
It being 2025, I don't have any envelopes, stamps, or buggy whips around my house ready to put into use at a moment's notice. Additionally, anything that requires actual mail typically also requires tracking and/or a signature on receipt so I can prove that it was sent and received...your $0.48 isn't going to cover that, and the time taken out of my day to run down to my local USPS to make that happen.
Going back to paper filing as a default is regressive, and involves more expense, labor, and time on both sides to make it happen.