If the leading edge of the deck is tilted too far forward, it takes too steep of a cut on your grass. This results in an overload of large grass clippings being created all at the exact same time. These may clump together and cause unsightly grass clipping piles on the lawn instead of being evenly dispersed and blown away smoothly from the mower.
People who want the best looking lawn possible may try to achieve the perfectly striped look often seen on baseball fields and on public property on their own grass. To do this, the mower deck has to be pitched appropriately. Most manufacturers recommend that the deck be pitched about 1/4 inch down at the front. A tilt that is too severe, or a tilt that goes the other way, can result in a mower that doesn't cut produce perfect stripes.
The deck on most mowers is designed to ride at a very specific pitch. Always check your manual to find out what pitch that is. If it is set too low, it could cause problems that result in components of the mower getting damaged or wearing too quickly over time. An extremely low pitch can cause potential problems when mowing over rough ground because this can cause the mower to dig into the lawn's surface on uneven terrain. This could easily cause damage to the mower, especially if the practice is repeated often.
If your deck is pitched too far forward, you end up cutting more grass off than you really should. This isn't good for your lawn. If you cut off too much grass, you make your lawn more susceptible to problems such as weed incursions. This creates care problems that can last throughout the season. Don't allow the mower to cut off more than a third of the height of the lawn. If the cut is excessive, the problem could be related to the deck pitch.