When you make jam, you change the taste and texture of the fruit in several ways:

• Squishing the fruit makes it into a more consistent texture, suitable for spreading.
• Adding sugar makes the jam sweeter, and also much less healthy.
• Heat changes the flavor of the fruit, With more volatile flavors evaporating.
• Heat evaporates some of the water, thickening it (reducing).
• Heat releases pectin, or you add additional pectin, which gels the jam.

Some people make freezer jam, which skips the heated steps, and gives you a flavor much closer to fresh fruit. Because it hasn't been cooked thoroughly, you need to store it in the freezer, but since freezers are a thing now, that's not a problem.

We can go a step further, though, and just use frozen fruit. Take frozen raspberries, defrost them, and squish them up with a fork:

This takes about a minute for defrosting, 10s for squishing, and is far superior to jam. Not so sweet, better flavor, and it's cheaper [1] and healthier as well!

Being able to store traditional jam in the refrigerator once you've opened it is an advantage, but I think it's a temporary one. Over time, I expect households will shift towards more freezer space relative to refrigerator space, as the quality of frozen food continues to rise. We got a chest freezer soon after we bought our house, and I'm glad we did!

[1] Our grocery store has raspberry jam for $2.75/lb, frozen raspberries for $4.39/lb, and jam is ~40% fruit. Though since we have the freezer space like raspberries a lot I've been buying them online, 30lb at $3.08/lb shipped. A shipment fills 6-8 one-gallon ziplocs depending on whether it ends up mostly whole or mostly pieces.