Its unrealistic to expect people to suddenly learn new skillsets later in life, especially if they have decades invested into these skillsets. I think this is why non-competes in many industries are ultimately unenforceable and why the courts or state legislatures never want to make non-competes powerful. People aren't machines. They can't really be retooled. If I get a job with Bigco and then switch to Smallco, Bigco shouldnt be able to tell me I can't be a programmer there. Corporations shouldn't have this level of power over us.
Even if we dismiss the first scenario as a 'business sale' I'd argue that sole proprietor businesses or any business with only a few people is much closer to being an employee somewhere. You can't expect someone to give up their only skills for 5 to 10 years for a modest sale. Not every sale is a SV-like billion dollar plus sale.
Yes, it's practical. If the non-compete is explicit and part of the conditions for the sale, the owner-seller is supposed to factor that into her selling price. E.g. if the owner has a mental price of $2 million to sell the furniture business but is unhappy about not being able to open another store, she needs to raise her price to $3 million to be content with not competing. In other words, the buyer of the business is partially paying the previous owner to not compete -- for a limited time such as 5 years.
Maybe you're thinking of employees and their unenforceable non-compete clauses trying to prevent them working for competitors in California. That doesn't apply to the owners selling their businesses.
When you're selling a business, you're selling the future. If you sell your furniture business, then turn around and open up a store down the road, you're attacking the ROI that you projected going forward and the buyer acted upon in good faith. Sketchy.
Employees are a different matter, as it's a one-sided arrangement where the employee has little bargaining power. Small businesses are different -- both parties are free agents.
We were once there to buy carpet; she's wheeled up to us in her cart (she had to be 80+ at the time), nearly hit my little sister and basically said "what price do you need to purchase this carpet today?".
She was famous for running the sales floor, even though she could have long retired prior.