Oh, com on, IKEA"s are deliberately designed as a maze. Yes, there are 'semi-hidden shortcut passages' and maps, both required by the fire department, but they also are deliberately obfuscated. The name of the maze game seems to be maximizing impulse buying, not just by forced exposure, but also gamed to the psychological effect that when on the threshold you will grab it 'now' anyway as you will never find your way back, and once in the cart 'dumping' it again in an 'inappropriate' place is something most people don't do.
IKEA has an almost Disney-esque level of "magic" and ability to become an expert in negotiating their space while pleasurably manipulating casual shoppers. IKEA can be a super efficient experience if you're in the know but it takes a bit of work - I suspect this actually endears them to both types of shopper, and anyone who sees through it and hates it stays away.
The shortcuts are signposted, and maps are available to take with you at the entrance - no other big box store does that, so I doubt it has anything to do with fire departments. Impulse buys greatly benefit from immediate commitment, so Ikea does a good job of not having pesky sales assistants everywhere. You have plenty of time to cool off about that silly table till you get to the warehouse.
