The game beckons a lot of things, I agree... and often its 'beckoning' feels more like handholding, but I digress.
I'd still disagree that it doesn't make sense to take the perks. Couple reasons.
Each to his own. My first mage took the perks and refused to enchant and only wore the archmage robes. At about level 38 (destruction skill 70), I was starting to become disappointed because I was about to get my expert level perk and still could not cast my Adept level spells more than twice without reaching for a potion. I am too much of a subconscious min maxer (did not need to write down my scores in Oblivion to level efficiently, just did it subconsciously, couldn't not do it unless I made a real effort to gimp). Started a new mage and went for enchant in lieu of cost reduction perks and was much happier.
First, getting to 100 skill in anything takes a substantial portion of the game, unless you're grinding. I have played a bunch of characters since December, when I got the game, and have yet to see 100 in any skill. So, getting to the point where you are freecasting by playing the game normally, there's a big stretch of the game where you could benefit from those Destro perks.
I did not "grind"
per se but I did do a lot of soul trapping and enchanting, mostly for money so I could pay for some training (I trained pickpocket to 50, for instance to get extra pockets). I was 35th level with my second mage before I got enchant to 100. Yeah, there were times when it would have been easier with a couple of cost reducing perks, but those first 35 levels were not that hard.
Second, aggressively levelling your Enchant is a good way to make sure the scaled enemies start to outpace your ability to deal with them. I suspect this is part of the reason people have trouble with Destruction.
Yes, and paying to train my other skills contributed to this effect also. Made the game more fun.
Finally, you can only walk around with so many enchanted effects, even with the double-enchant perk. And other passive effects, especially resists, are pretty nice.
It's fair enough to say that freecasting was intended; my real problem isn't with your argument so much as it is with others who complain that the only way to play a Destruction mage is by getting casting costs reduced by 90% or better. My own experience shows me that that's not the case.
I think the 50% from the perk alone is not enough, but the perk plus another 25-35% from gear is probably enough to be a decent destruction mage. If I had an Immersive HUD option on the PS3 I would probably run at about 75% cost reduction for Destruction/Restoration with three pieces of gear and 50% in Illusion and Conjuration with two pieces of gear (one of those being a Falmer Helmet). Then I would have plenty of perks to do what ever I want, having saved 18 cost reducing perks.
But since I loose my magicka bar when I turn off the HUD, I usually run with free casting in Destruction/Restoration and a 25% reduction in Illusion/Conjuration. I don't cast many spells from those schools anyway (I have a different character who uses Illusion/Conjuration), and the only alteration spells I use with any character are candlelight and magelight (and very rarely detect life or water breathing). I don't particularly like free casting but I also don't like having to guess at my magicka bar either.
Guessing at my health bar is bad enough, but with free casting I can heal whenever I want, so it is no big deal to waste a few healing spells. I suppose I could just waste potions, but that seems like a waste plus I have to stop the action to take a potion, plus there is no drinking animation, so it feels really cheap to spam potions. At least with a healing spell I need to break away from the action enough to be able to cast it.