I didn’t design the system. It’s just how it works.
Obviously they don’t actually form the government over the weekend they know who they’re going to have in various positions because they’re already in the shadow cabinet positions. It exists because historically the MP who are now cabinet members, and therefore required to live near the capitol, may very well actually be in completely different parts of the country and it would take them a few days to get back to London.
Especially the government suddenly called an election like they’ve just done.