Yes, all the cats that I've had are like that. I think the back ones wear down more easily for one thing, and for another, they need longer claws in the front for climbing. When Mingo's back claws get too long, he chews them down himself.
Cats rear claws are semi retractable... they wear down more than fronts.
Paw anatomy is REALLY interesting......Front and rear paws are very different. When the paws are relaxed and the toes are not spread, the center two claws on the rear are parallel, and on the front paw the center two point in towards each other. If you can get your cat to cooperate you will find that when the front toes spread,and the claws are out, they form a perfect half circle: ideal for gripping prey (or fingers if your cat is not happy about you poking at its paws!) The rear claws, when spread, stay more parallel to each other, ideal for traction when running.
The front claws are retractable so they stay sharp for hunting, and make less noise when stalking. The retraction mechanism is complex and very flexible to hold prey. The rear claws/toes need to be more robust because of the high stress of getting traction when accelerating and running... those huge hind leg muscles produce a lot of power! Consequently, the retraction mechanism favors strength over flexibility and full retraction. The compromise is a claw that sticks out a bit more and gets worn down when running/climbing. When worn or trimmed properly, the rear claws do not touch the ground when stalking to keep with the stealthiness of hunting.
Makena's front paw, you can see the two middle toes/claws point in together
Front paw spread, claws in half circle
Makena's back paw, toes spread for traction, middle claws parallel
Okay, looking at what I just wrote... maybe a bit dry and only REALLY interesting to me!
Cats' claws grow in layers like the rings of a tree. As a cat's claws get old and worn, the outer layers shed away and a new, healthy layer comes in from underneath.
Sometimes, cats will chew their claws because they feel the outer layer starting to shed and they want to make it come off faster. Other times, a cat's normal scratching activities will pull the layer's off naturally.
If you look around your cat's scratching places, you'll probably find shed claws.
Casper chews his claws sometimes but his favorite thing is to just "go to town" on one of his scratching posts. He really likes to dig in his claws!
We saved a couple of Casper's shed claws and whiskers. We put them in a locket with his picture so that we'll always have something to remember him by.
I would think it also has to do with the way that the cat maintains the claws, in addition to the excellent explanation offered above. Mine scratch to deal with the front, but for the back claws they periodically chew them down instead. I think many cats do it this way? It makes sense; they don't need to be quite as sharp as the front ones, and keeping them shorter keeps them out of the way.