Etrian Odyssey II, like its predecessor, wears its inspirations on its iron-plated sleeve. It's beyond obvious that the game's creators absolutely loved the Wizardry series. Despite the conventions injected into the role-playing genre by Square Enix since the days when painfully difficult RPGs were the norm, Etrian refuses to let go of the past.
To understand why Etrian is the way it is, you have to first understand its roots. Back in the early days of PC gaming, most games took direct inspiration from Dungeons & Dragons. They lacked the technological magic to replicate the experience in the same way a Baldur's Gate would years later. As such, the most revered games were typically grid-based, first-person dungeon crawls where almost every enemy could kill you instantly and maps were almost totally unheard of.
In order to succeed or even merely survive, players were forced to grind untold numbers of baddies and construct their own maps on sheets of graph paper. It's since become a bit of an in-joke amongst nostalgic geeks, but really: That's how many gamers spent their free time back then.