Why do more people play beta than alpha?

As the title says, im trying to understand. What is the core thing keeping people playing beta 1.7.3 compared to alpha 1.1.2 _01 (might have got that wrong mb). The neon green grass/leaves are nicer imo and definitely more iconic of early minecraft, and the only core feature that i can think of that is missing is beds. So, what is it that keeps people playing beta? Is it the additional biomes and log types?