What do we use the Backhoe for? For digging.... not so much. Oh, it digs easy enough, but frankly we only dig holes or trenches a few times a year. In a year we might plant a few 8 foot trees bought from the tree farm. Or maybe cut down a few mature trees. When we cut one down, the hoe plus thumb holds the trunk out horizontally at the right height for chainsaw sectioning and limbing. Afterwards the bucket removes the stump.
For carrying 12 foot sections of tree trunk down a narrow six foot path there's not much that is better than a backhoe and thumb.
Maybe once or twice a year we will repair or put in an underground line that requires a trench. It's fun and easy to dig the trench in an hour, but frankly we could do the digging just as well by hand in a couple of days if the ground weren't so rocky and we were a bit younger. The backhoe simply makes it easy. But I wouldn't say the backhoe is a necessity. Before our first little used 3pt backhoe, we did exactly the same work with shovels, levers, and rockbars. My recollection is that the work was enjoyable. We never felt that we were being put upon. Nor did we miss the backhoe that we had never owned.
So that's about it for digging. We actually use the backhoe more for lifting, placing heavy things carefully, or as a small mobile crane and grapple. In that mode we use it all the time. With the thumb the hoe is like a precision grapple that has a wider range of motion.
A lot of what we do looks a lot like landscaping, and it can involve rocks. I'd say that the ability to lift and place or flip and roll rocks around is another whole reason to have a hoe. And like craning, it doesn't have much to do with digging.
Something that only you can decide is how you like to do projects. I'm impulsive. When a day comes along without outside obligations, and I feel like doing a project then then being able to fire up the tractor complete with backhoe and thumb means I can immediatelybegin to enjoy the work. Being able to do that on the spur of the moment is worth a lot to me. It's worth far more than the price of the hoe.
If on the other hand you are the kind of person who has a lot of control over your time and who likes to plan every detail of a project including the renting and fetching and returning of equipment one day so you can work the next.... Well, if you get your pleasure from working that way then there's no reason to own a backhoe. Or in fact to own a tractor at all. You can just rent. Nothing wrong with that, either.
As to the cost of the hoe. It doesn't have to end up costing much because it is an investment.
I like to buy tractors new and implements used. A good used 3 point backhoe bought for a fair price won't cost a thing to own. They are just about bulletproof and easy to sell used. We've had three, and always found that I could get most or all of what they cost just about anytime we wanted.
A shorter answer to your question about backhoes is that as we get older we use it a lot more. It enables us to do the same work we could when young.
rScotty