I tend to hike solo a lot b/c of many reasons. Mostly b/c i am very spontaneous. I like to hike on sunny days, when the sun is shining and it is warm. In the Champlain Valley, the weather forecast changes every hour, either there are many weather patterns that cross here or the meteorologists are terrible, not sure which one is correct. But, yeah, i would rather not hike in the rain. It is also difficult finding people that hike the same distance/speed as me.
And to be honest, the real reason is I like to be alone and absorb the spirit of the wild. I have never been one to follow religion but I feel something spiritual up in them there woods and it slows down my world and my soul into a natural rythym. I go to the mountains to escape the "noise". If i hike with someone that is chatty Cathy about the latest "The Hills" episode, then that kinda defeats the purpose. So maybe 40% of the time I hike with others, but i really enjoy the solo time. I like to take the time to look into myself and figure out who i am, and who i want to be. The solitude does not freak me out, I figure if there is a higher spirit that determines it is my time to get attacked by a bear, then hey, it's go time. My solo drive to the trailhead is probably more dangerous than a random animal attack or a slip and fall.
With others or solo, I love hiking. Both are different experiences. I am not saying one is better than the other, but my best hiking memories are of both. Do whatever floats your boat, just let the tide take you where it may.