I've taken enough solo and group trips to accept that there are good and bad parts about both kinds of traveling. Solo travel can be great, fulfilling, flexible, and rewarding in many ways but there are downsides. For me, the following were the downsides of solo travel (and let me preface by saying that none of these are unsurmountable and can totally be overcome by meeting other people/joining up):

1) Having to pay full price i.e. not splitting the cost of airport taxis, day tours, hostel rooms (if you're looking to get a 2-3 person room). In addition, often activities like diving, canyoning benefit from having group discounts.

2) Being in charge at all times of organizing your trip. Need to figure out directions? You got to do it. Need to figure out which coach on which train goes to which little German town? You got to do it. Need someone to wake you up to catch that early flight? Its all on you.

3) Getting drunk/high/nightlife - you have to take of yourself. While you often end up going out with others, in the end, you've met most of these people maybe a few hours earlier and perhaps are not ready to show them your most inebriated self yet. This is also sometimes more of a problem for female solo travelers.

4) The pressure of socializing. After a few weeks of traveling solo, it does become tiring to have to enter each new hostel and push yourself to make friends - you have to repeat the same "where are you from, what are you doing" story, get to know each other, build a semblance of a friendship - and after a while, it does becoming tiring.

5) Taking photos. Unless you want to invest in a selfie stick, you rarely have photos of yourself or need to constantly ask others to take photos of you.

6) Getting sick. Being really sick and on your own (especially for the first time) is pretty rough. I got bit by a snake in the Peruvian Amazon on a solo trip (as in with others, but not people I knew from before) and I remember just thinking I'm going to die here, alone, thousands of miles from friends or family.

7) Having items to share. Especially relevant on big mountaineering trips or camping trips, its far easier to borrow a pair of socks or toilet paper from a close friend because you forgot to buy some at the last Nepali village, than from a relative stranger. Its easier to ask someone to borrow their solar charger because you are at 5% while they are 10% battery, because you know you've known them for a long time. But the biggest one of this one, by far is borrowing money. Did your wallet get stolen? Did you drop your only working credit card from your backpack and now your backup card doesn't work in El Calafate (happened to me)? Did you not budget enough cash withdrawal to tip your porters and are now half way up a mountain? Definitely easier to borrow from a friend from back home.

To end this post on a more positive note, having said all of the above, solo traveling has contributed to some of the best experiences of my life. Whether its a short trip to Chicago for a weekend or taking an impromptu flight to Russia to climb Europe's highest mountain, solo travel can be extremely fulfilling, and really makes you an independent, hardy traveler who can fit into most situations, while taking care of himself/herself.

And all of these "issues" can totally be solved by meeting and making friends with people you travel with. In fact, I've been in all of these situations and gotten out of them by the generosity, kindness and empathy of fellow travelers, most of whom were complete strangers only a few hours ago.