Exterior Exposed Wire

anyone with dull pair of scissors can come up to the side of the house and cut it and keep moving without anyone knowing. If my alarm system ran through the internet, that would be to weak point to exploit.

True, but anyone who is going to this much work to defeat your alarm isn't going to be stopped by a little bit of PVC, either.  Bolt cutters come small enough to conceal.  A good alarm system will notice lack of connection.  Assuming it's monitored, they'll act on that.  If it's not monitored, then you'd need cellular backup.

@dave006 Than the issue isn't wanting to make the drop secure, at least secure in his eyes.