Many reasons...
I would imagine there are as many reasons for leaving the business as there are for getting into it in the first place.
Some SPs do it for a short time to pay off loans or raise some money for their future plans. When they reach their goal, they move on with their lives.
Others are in it because it's a good way for them to earn a living while they are single, but they (and/or their partner) may be uncomfortable with this line of work when they enter a serious relationship.
Some SPs may decide to retire when they find the effort of working to not be worth the income. Perhaps their business has dropped off or, maybe, they have other (more mainstream) business on the go and they prefer to focus their time on that.
If an SP retires because of time retrictions, she may still be interested in working part-time or occasionally for regulars. I've known some who fall into this category too. Usually, they retire altogether as their regulars move on and they don't seek out replacements. Other times, they come back to the business when the time allows them.
I'm not an SP so that for every reason I've been able to give, there are probably hundreds that I haven't thought of.
Zog.
