alt Hacker NewsThat's a contingent fact about the place and era you live in. Medieval peasants - the majority of people who have ever lived - were not dumbasses, not all of them - but there simply wasn't a way for even the smartest to accumulate long-term wealth. At best you could maybe get your neighbours to owe you a few more favours, and maybe once in a generation if you played every card right there might be a chance for a patriarch to acquire one more piece of land, but that's it, that's your lot. (Sure you can work your ass off and produce a bit of extra grain in a given year, but then what? It's going to rot, and selling it for money is surprisingly useless to you)
Money was useful - not as much as today, sure. But traders and tradespeople existed in the middle ages, so you could buy some goods and services. Metal tools and farming implements, harnesses for horses or oxen, pots, clothes / fabrics, maybe woodwork for a house...
Some of these things you could make yourself or were commonly self-made instead of buying, but that, too, requires planning and discipline.
I'm a bit shocked that some people think of medieval life as something like Elbonia in Dilbert comics. Heck, I even find the middle ages a pretty boring time in human history, but I know enough to understand that it wasn't as simple as "everyone lived in the mud and ate mud".