I’m not sure how or why grape became the default. For the longest time, I thought I didn’t like PB&J. But ever since trying it with strawberry instead, I understood the appeal. It’s so much better, and now I find it weird that the combination isn’t more common.
I’ve never noticed grape being default. Maybe it’s regional? Restaurants here still have the carousels with a variety of jams if you order toast.
But yeah you’re right. I think Raspberry is also top tier, and my own Evan’s Cherry tree jam I make.