It's worse than that.
Yes, you can pay for a streak freeze. If you don't, you'll probably find that you were given one for free anyhow. You'd have wasted your gems.
Yes, you can pay to undo a streak loss. It's more than paying for a freeze.
It'll give you multiple chances to pay for all that, too. If you're out for days and then come back, you can pay to fix your streak.
What is the point of a streak if you can just buy your way back to it?
Also, I had paid for the last couple years, which (IIRC) includes free streak freezes. It still asked if I want to pay for them. I'd say no, and find I had one anyhow, or a friend had miraculously given me one.
But during the last year (365 days) my streak was actually only at 190 or so because I'd used so many streak freezes that I got for free. I wasn't even trying to keep my streak.
When I finally let my streak die, the icon started trying to guilt trip me into coming back with horrible icons of Duo being sad, heartbroken, or even dead.
The constant mental manipulation that was well beyond what gamification should ever be was what finally drove me to just quit playing altogether. I had already canceled my sub long ago, but I'm not even going to use the remainder of this year I've already paid for.