Question about Recip Blocks

[rblight]

I have that noticed a lot of Linkmasters have started adding a rule that forbids any recips to have outgoing links to more than one domain. Most will have one to the main directory and one to a specific niche section of the link list.

Of those of you who have such a rule, what is the basis for it. It strikes me as a practice that would benefit list owners (ABC linking is considered better than recip linking), not so much for free site submitters, who will lose more link juice.