A plumbing business doesn't have "assets" though; it's valuable because the owner is good at their job. You can't durably "sell" that brand value unless the new owner is also known to be great at their job, at which point they don't really need to buy your business.

Family businesses handle this by slowly getting the next generation involved, such that the intangible value has been transferred by the time the owner wants to retire. That works less well with a stranger. You really need high levels of trust to make that work fairly for both parties.