No reason in particular, but I like it because it breaks the work-from-work week up.

The important thing is that the whole team is WFH the same day so we can depend on other days for meetings and whatnot, and nobody feels left out when they are WFH.

Probably so it's not treated as a weekend, and so that any issues that arise can be discussed on Friday.

Don't WFH days feel the best when they're in the middle of the week? That way they break up the 'daily grind' feeling and give you the opportunity for deep work right in the middle of a weekly sprint.