There are many reasons to the popularity of Karwa's bus service. First, the fares are cheap and affordable by most residents of Qatar especially those who fall in the lower income bracket. And they form the majority of the population of Qatar. Second, the the timings are fixed. This allows one to plan ahead and be at the bus stop some minutes before the bus arrival. Third, the buses are safe. One hardly sees any Karwa bus involved in an accident. Fourth, the system of payment of fare is rather easy. Lastly, the supervisors at the main bus station are very helpful and out to guide travelers in the best way possible. Not just that, they listen to customer complaints and take immediate action on any incident.
Having stated the above, there are no doubts there exists some room for improvements. I have two in mind. First, Karwa needs open some more places where one can get his card recharged. They should have one recharging point at Malls. There was just one place in the area where I live and it is so far that I find easier to recharge at the bus station than walk several kilometers for recharging my card. Second, there is a way by which Karwa can cut down it's operational costs by at least 30% if not more. I believe I know how but I guess the management at Karwa will need to scratch their heads on this to find out.