My reasons (not in order)

1, The fun ; You cannot beat sailing down wind with the kite up, on the wire in a cloud of spray

2, The adrenaline rush; sailing in big winds is really something else

3, The people; sailors are the bet people on the planet (a close second comes skiiers)

4, The challenge; I truly believe we do the hardest sport in genearal terms; we have to be fit (ish), we need to understand the conditions (ish) and we need to understand the technology.

Yes, doing triathlons is harder physically
Yes, Surfers can read the waves better than we can
Yes, F1 is more technical.

5, The challenge of always knowing you could have done better. I don't believe anyone, ever will have a perfect race.

6, The people, did I mention that ? I still know people I met 28 years ago when I started sailing, we've shared the good times, the great times and the bad times and the sad times.

7, Just being out on the water, be it racing or taking people out for a blast.

8, Did I mention the people ?