Is there a particular reason for this?
...
I am curious as to your reasoning - could help me tremendously!
It was a bit tongue in cheek, but yes, I have some reasons, and it is very much related to the reason people who do Salesforce (and SharePoint) are in big demand and are headhunted.
This is going to be a bit opinionated:
Companies that use either (or both, they are not exclusive) tend to be big corporates. Big corporates pay well, so it is hard to get someone to move unless you offer them lots of money. Good devs in corporate command a lot of money, partly because mediocre devs can often find a "safe space" to be mediocre but still get paid well.
Now Salesforce devs... Salesforce (and Sharepoint) is not "real" dev work, ie, not the green fields/blue sky fun startup **** developers get excited about.
It is much more mundane, much more constrained by both the platform and by what the giant corporate wants you to do for them.
In short, you can become a Salesforce dev, sell out job satisfaction for high salary, and be tied to that role because you can't afford to be paid less. Your only hope is to become a good Salesforce dev, in which case you may be able to buy happiness outside work with the cash you make grinding away your self respect on the job.
Your mileage may vary, though.
Just don't choose PHP dev as an alternative