Why run/walk after 20 min. run?

[YikesMn]

I'm curious as to why the program goes back to runs separated by walks in week 6, after the 20 min. run at the end of week 5. I'm going to continue as suggested, but this particular point in the training is baffling. Ok, part of me is curious, and another part of me just wants to continue having the satisfaction of completing a non-stop run. It was fantastic.

[KeepTrying]

I'm not sure either why this is the case. But it seems to work for most folks - so I just did what Coach Claire advised. However by week 7,8 and 9 I was feeling ready to extend beyond 30 mins - so I sneaked in some longer runs then.