Tallg,

If I had to guess, I would say the reason is that Qatar Airways is more focussed on clawing market share from rivals (Emirates, Etihad etc) than it is on fostering a Doha-as-destination tourist industry.

Qatar Airways does offer Doha as a stop over destination. I can't imagine any tourist coming ONLY to Qatar for a holiay. Perhaps they might stop here on their way to a more established tourist destination, such as Muscat or Dubai.

Regarding the question about flying to Doha from India on a ticket bound for Dubai:

Assuming you carried your luggage and had it with you when you arrived in Doha, and assuming you had the required visa to enter the country, then there would be just one small problem - your return leg would be cancelled because you didn't board the Doha-Dubai leg. The result would be that you would have bought a very expsenive one way ticket, rather than a very cheap return one.