It is incumbent on every farmer these days to produce as much crop profitably as possible on the acres that are operated. An improper sequence of crops can lead to disasters of monumental proportions, when you forget which crop protection product you used on a particular field last year, and you wind up losing an entire field due to herbicide residue or a forgotten disease incidence. Rotations can often be a money saving plan when utilizing inoculated pulse crops followed by cereal type crops, realizing the savings made possible through the extra nitrogen left by the pulse crop. Rotations also mean a change in herbicides, to enable you to get away from using the same group each and every year, and some even give you an added benefit of having a slight residual for the next years' crop. Anything that can help on the input bill next year is always welcome.
Rotations can also mean timing in seeding a field.
If you seed the same field first in order each year, you will give the advantage to the competing weed populations, because they think they have you fooled. This eventually will lead to a certain species of weed always present in that field, because you have eliminated most others. Field diagnostic walks will show this single weed species very often, and the farmer will not likely know why. Be aware of the quality of the seed you are currently using and plan to use for next springs' seeding. A germination test is always the minimum that should be done on a sample of cleaned seed.