Detect has problems with range and the cooldown. Like in Shatter, it was impossible to find a NIN unless you already saw them hide; the range was too small and the environments too large. And surprise, eh; the problem was even when you knew said ninja was doing that, you couldn't be prepared for stealth, because it rendered them untargetable. You can check behind pillars from a distance or just run away from obstructions. Hide was the gift that kept on giving, in other words.