I almost feel like the reason for Hashirama being so laidback and carefree is to make a reference to Naruto who has the same personality. And yes Naruto is passionate for his friends/allies, but he is always pretty jokey and laidback in the village. The last chapter kept referring to Hashi as "the God of Shinobi" and I feel like it's symbolism to Naruto who will soon take his place as 'the strongest'.
Besides, that's a pretty common theme in Animes.. Luffy, Goku, Naruto. The main characters are often kind of dense, funny, stupid, but passionate for their friends and can get REAL serious when the need arises.
EDIT: Lol, I only read the first page then realized the guy above me basically summarized a lot of what I said in 1 sentence.. xD