Here are the top 5 reasons to invest via SIP:

SIPs give a disciplined approach to investing:

One of the major benefits of investing via SIPs is that they help in cultivating the investing habit.
As you have to invest a fixed amount monthly, you develop the habit of regular investing over a period of time.
Furthermore, these investment amounts need not be huge. They can be as low as Rs. 500 – Rs. 1000 per month.
Some SIP schemes that have further lowered this bar by enabling people to invest as less as Rs. 100 per month. This way you can invest at least something each month without ever feeling any pinch in your pocket.

Majority of the people invest in SIPs with long-term goals like buying a house, children's education, retirement etc.
As it is difficult to cough up such huge amounts in one go, it makes a lot of sense to build a corpus over a period of time by making regular monthly investments.
In addition, although it is recommended to invest via SIPs with a long term perspective, there is no lock-in period. You enjoy complete liquidity and can withdraw from the SIP anytime you feel necessary.

Investing in SIPs yields better returns as you remain invested for longer period of time and hence compounding is easily the biggest advantage.
The earlier you start investing with SIPs, the better it is. Even if you save Rs. 500 or 1000 per month, your investment compounds over longer term and gives you an advantage for wealth creation.

As investing through SIPs involves making a periodic investment in the equities through equity mutual fund, you're able to ride through the ups and downs of equities with great ease.
When the market goes up, you earn fewer units and when it falls, you receive more units. Resultantly, as you continue making investments over a period of time (regardless of the market situations), timing the market becomes unnecessary.

The conventional wisdom says that it is never a good idea to keep all your eggs in one basket! It is all the more applicable to the investment domain. Most experts encourage investors to buy blue chip stocks and diversify them across at least eight to ten sectors.
A major advantage of investing in mutual funds via SIPs is that one gets to enjoy the benefits of diversification even with small investments. Hence, the risk gets spread out and you make the most of the gains from different holdings.