Different strokes, but let me create what I believe is a common scenario:
Turn 3, you're on the draw. You play your third land. Your hand is: Island, Swamp, Take Inventory, Gideon, Sorin.
What's your play?
I'm having a bit of troubling understanding this scenario, tbh. If I'm on turn 3 on the draw, I should have drawn a total of 10 cards, including the opening seven. Here, only eight of those are accounted for. If I'm playing aggro, maybe I played Blessed Alliance on turn 2, or I could have played Jace out on turn 2 and had it killed I suppose, but that still leaves one card unaccounted for. I almost certainly would have played Take Inventory on turn 2 if I'd had it, so presumably it was my draw for the turn, or I found it with Telling Time, or I already played another Take Inventory on turn two. Do I have my colors fixed for Gideon next turn? Does my opponent have a board presence? Are they likely to be playing permission, flash creatures, or evasive creatures? How much do I suspect they've got a turn 4 Planeswalker (quite a bit I suppose, if they have shown green mana and don't have a board presence after their third turn)?
If I strongly suspect they have a planeswalker, I suppose I'll just pass the turn and bluff permission (assuming I've got double blue for the threat to be credible). Other than that, I play Take Inventory. A smart opponent will play something useful into open blue mana, and will gain a tempo advantage over me if I bluff instead of playing my spell. Tapping out lets them play their best four drop, which isn't ideal. If they play out four power worth of attackers or greater, then I probably can't safely play out Gideon, and have to plan to dig for a sweeper as quickly as possible, with the back-up plan of using Sorin to gain back some life and remove their most dangerous attacker to buy time. So a lot there depends on what I hit with Take Inventory and my Turn 4 draw step.
However, this is a bit of a slanted scenario. I have personally won a lot of games because of the card advantage I've gotten off of Take Inventory, and even at instant speed, three mana is an awful lot to play for card selection rather than card advantage. I'm running ten 3 CMC cards already, and if I switched out take inventory for Artificer's Epiphany, I'd have a lot of situations where I had no play on turn two, then want to actually cast an answer on turn three, leaving Epiphany stuck in my hand at least until turn 4, by which point I've lost a fair bit velocity already. It really is useful to be able to use your second turn rather than waste it.