1) It inculcates the discipline of regular investment.
2) Because of the regular investment, one invests a higher amount at the end of the year
3) You need not time the market.
4) You get the benefit of rupee cost averaging. i. e. You get more unit of a mutual fund if the price of a mutual fund unit (NAV) goes down. You get less number of mutual fund unit if price of a mutual fund unit goes up.
5) You can start and stop SIP any time.