As much as I hate to admit it, most (but definitely not all) Congressman, in the past and present, only care about getting re-elected and not about serving the people. Yes, many Congressman do things that satisfy the people, but not because they want to fulfill We the People's wish, but only because they want to be re-elected.
By limiting the amounts of terms a Congressman can serve, it will encourage those to run for election who actually want to serve the People and push for our ideas to become reality.. A good example showing how our Congressman we elect to "serve" us dilly dally is the Fiscal Cliff Bill that was recently passed. They had MONTHS to work on this, but instead shrugged it off until the last minute, creating a complete, yet poorly compromised bill.