Why do so few mail providers support Port 587?

Speaking on Deep Background, the Press Secretary whispered:

Okay, the main difference seems to be:

1. People here trust, that mailservers on port 587 will have
better configurations than mailservers on port 25 have today. I
do not share this positive attitude.

Well, is authenticated SMTP 587 going to be worse than open port 25?
I doubt it, but... In fact, I think most folks will do way
better. Call that blind faith in the inhabitants of Middle Earth
^H^H^H NANOG....

2. Port 587 Mailservers only make sense, when other Providers block
port 25. My point is: If my ISP blocks any outgoing port, he is no longer
an ISP I will buy service from. Therefore I do not need a 587-Mailserver,
as I do not use any ISP with Port 25-Blocking for connecting my sites or

So you will choose hotels, conferences, etc, by whether or not they
block 25?

And coming soon.. airlines!

  "That's right: aisle seat, low-sodium meal
   and NO port 25 blocking..."

I do well to find out if the above has access at all, esp. if dealing
through a reseller [hotels.com, etc].