The main reason for buying should be the fact that it is a great technology and even its haters confirm it.
Here is the big deal here. Bitcoin even without its high price still the most convenient currency to use with in dealing on our money, whether to send and receive because it's technology really giving us a no hassle experience in terms of payment.
But with the price increase, many takes this as an investment which also brings good output to this currency as we see it today.
Yup. Many people here say Bitcoin is good and great because the price has gone up nicely in the last months. But as you also said, Bitcoin is great in many aspects regardless of the price. Some people need to realize that.