You reasoning clearly demonstrates that you have a very specific gamestyle in mind, and you're still unable to see or willing to accept that other people prefer other gamestyles and they are not "wrong" (which style is more popular I cannot say, maybe your style is vastly more popular than mine, but from my little perspective I see our gamestyle all the time because obviously it's the one we use...).
You are stating that something which is a challenge for a 1st level character should not be a challenge at all for a 20th level character. Correct me if I'm wrong, but the message I get is that
everything which is a challenge at 1st level should be trivial at 20th. This is one gamestyle, and AFAIK it's a design assumption of 4e.
I am stating that in my gamestyle something ceases to be a challenge only for those characters that choose to get better at that.
The idea that challenges get harder as you level up is only half of the point.
The other half of the point, is whether the game should leave behind those who don't invest in a skill or not, and in this regard 4e
is different for example from 3e: the 4e philosophy (therefore the reference gamestyle) is that nobody should be left behind, thus IIRC everybody gets better at everything, and the difference between someone who invested in a skill and someone who didn't is bounded (e.g. roughly the same difference in % of success); the 3e philosophy is that if you don't invest in lockpicking, you'll never get better at lockpicking, thus that 1st level lock is always going to be a challenge.
These are two different playstyles, with 4e being more heroic so that everything becomes trivial at some point for heroes, and 3e being more gritty because if your party doesn't have a Rogue in 4e, well it's a nuisance but can be managed, if it's a 3e party then you have a problem. And here lies the key question: what is more fun, having a problem or not?

Well let me tell you that there is no answer to this! For some gaming group, getting stuck in front of a lock when you're all heroes saving the world is frustrating (apparently unless the lock if presented as "made by the gods", even if at the end it still takes a d20 roll with the same % of success), but to other gaming groups having
some things in the game here and there which blocks you, is a chance for being required to find a creative solution.
So it's not only a problem of individual PCs but also of the whole party. 4e uses its design solution to allow a party any combination of classes with minimal drawbacks. Don't have a Rogue or Cleric in the party? It makes a small difference, don't worry. More or less a 4e party is capable of handling any
type of challenge, although with varying % of success. This is very good for some groups. OTOH in my favourite playstyle this is not so good... because
I want sometimes not to be capable of handling something in the straightforward way (e.g. roll a skill check), so
for me a party of PC that can handle
everything is actually not as much fun as a party that sometimes is stuck and forces the players to find an uncanny way out.
Therefore, of course I want a Rogue who's investing in lockpicking to get better so that at 20th level those 1st level locks are a joke for her... but I do not want that to happen to everybody else. And if nobody in the party invests in lockpicking, I want the party to be still challenged by those rusty cheap locks forever (although as I said before, clearly this means only if they try to
pick those locks... an epic PC will have plenty of other ways to blast the lock away!). Having someone invest in lockpicking is a
choice in my favourite gamestyle.
I'm sorry if I'm not so good at delivering my point... check out also [MENTION=14506]Sadrik[/MENTION] posts which probably say it better