If the lie of a club is off by as little as a degree, this could mean that your shot direction could be off by 3 to 5 yards. You may not notice this in your long irons, but in your wedge game this could mean the difference between being in the bunker or hazard as being on the green putting.
Loft is equally important; there is only 3 to 4 degrees to loft difference between clubs as you progress through the set. If you had a 7 iron that was a bit weak and an 8 iron that was a little strong, you could in effect not notice much difference in distance between the two clubs.
Think about that for a moment, do you have two clubs in your bag that you hit about the same distance this may be why.
You should have about 8 to 12 yards different between each club; if you don't have that you may want to get them checked by a qualified clubmaker that has the proper equipment to correctly identify any of these problems that you may have.
Please be aware not all clubs can be adjusted for loft & lie because the material some manufacturers use or style of club head doesn't allow for custom fitting to suit your style of swing.
I have all the up-dated equipment to perform such tasks.