imho this article is a good illustration of how business get bought and not sold. The business has to be able to live on its own and be interesting to be bought. But that means you have less reason to sell
Accounting (consult your own accountant please0: when you make salary/profit from your small biz you get taxed at ordinary tax rate (up to 40% in the US) where is when you sell biz as assets you may be taxed at capital gain tax rate (0%-20%) which is a financial advantage - like you get paid 3-4 years ahead. Again, consult a professional on this.
You could have other ideas or projects you want to work on, but unable to because your business is your 100% priority and has been for too long.
You might not want to deal with hiring a team because that's the stage your business is at - too big for you to handle on your own or you don't want to work 60-hour weeks anymore.
I could just go on and on, but a combo of 2-3 of these will certainly make the thought of selling quite appealing to many.