Also the amount of scamming involved in the virtual currency market is pretty substantial. I assume they're doing this to curb the headache that's generated.
Or, perhaps Paypal is a company whose interests aren't well served by the availability of electronic money transfers with little or no transaction costs.
Now that's a conspiracy theory.
Just as a general rule: positing that one individual entity is acting in its own, legal, self-interest is not a "conspiracy theory". It may or may not be correct, but it's not a wacky, crazy, tinfoil hat conspiracy theory.
"wacky, crazy, tinfoil hat conspiracy theory" != "conspiracy theory" ;)