Levels are (currently) the only true measurement of progress that you have between players. They represent bragging rights, they affect the range of players you can group with and fight against, and they let you advance your stats.
The number of stats you can raise is dependent on your level, above all else. That number is calculated as follows:
From levels 1 to 75, you can raise 6 per level, totaling 450 stats. From levels 76 to 150, you can raise 5 per level, totaling 375 stats. From levels 151 to 250, you can raise 4 per level, totaling 400 stats. At level 251 and beyond, you can raise 3 per level.