I think you need go on yes, as none of those examples prove anything useful for the d&d system.
It may very well be that bilbo is actually a 4th level expert already, and that the other people were actually 2nd level experts/2nd level fighters, or 3/1, or maybe they were also 4th level experts.
Gandolf might simply be a 5th level mage, or maybe he is a 3rd level mage with some sort of racial LA.
Really, all of those can be explained away in such a way as to make it that the new comers are actually very close in level to the party level.
Personally, I can start play at any level, make a good background story, and run with it.
I greatly prefer starting at 3 or 5, that way i have enough levels to play with to make a good background story. If you are a level one character your background is mostly going to be about people other than yourself in all likelyhood.. because you simply have no experience.
There can be exceptions of course, but they are very few and far between (such as a character who has been level drained back to level 1).
The only difference between starting level 1 and level X is that you have more options of what to put into your backstory for level X, that is all. More options = good.