I don't know if you've ever had to do any significant writing on a manual typewriter, but it is a very difficult process. It would much, much easier to write it out long hand (he has great hand writing, as can be seen on his sign.). Even better would be to write it up o a laptop, let the customer view it on the screen, then email it to them later. Or, write it up on a phone with a $20 Bluetooth keyboard and email it immediately. Lots of different superior options exist, depending on his budget.
Bottom line, using a manual typewriter is a theatrical element and designed to draw attention to him.
You seriously think you can't type on a typewriter?
As to doing it electronicly, he deals with that issue, a electronic story email would have little value to most people.
----------------
My favorite exchange was between “I_thrive_on_apathy” and “dlins”:
i_thrive_on_apathy: What the fuck is he going to do with that typed page? Scan it?
Dlins: you do realize things have value even if they're not digitized, right?
while the typewriter may or may not be a convenient tool for producing hardcopy outside in a park, it's most definitely also for purposes of grabbing people's attention.
Bottom line, using a manual typewriter is a theatrical element and designed to draw attention to him.