What are the reasons people switch from vegetarianism to veganism?

Question

Many vegans I know have been vegetarians for some time, before switching to veganism.

What are some reasons for this? Why not going straight to veganism? Also, are there any benefits for not becoming vegan from the start?

This is not a duplicate of Reasons for being vegetarian or vegan other than ethical reasons? as this question is asking about the reasons people have to first become vegetarians and only then vegans, compared to going vegan from the start. As mentioned in the comments though, there is another question similar to this one. I still believe these two questions ask different things - this question asks for reasons that someone who already IS a vegetarian has, to become vegan, as opposed to omnivore considering veganism and thinking about vegetarianism as an intermediate step.

Answer 1

Vegetarianism is a diet that refrains from consuming the flesh of animals, sometimes for religious, spiritual or ethical reasons, sometimes following tradition or culture, and sometimes for health concerns.

People who had become vegetarian on ethical grounds in an effort to avoid being personally responsible of harm or cruelty to animals, may later learn about the harm and cruelty involved in animal farming practices other than meat and fish, such as egg, dairy, down, wool, fur, leather, research and entertainment, and adopt a vegan lifestyle as a result.

Many omnivores who wish to go vegan prefer to do it gradually, by reducing consumption of meats at first, go vegetarian later, and ultimately become vegan.

Different people have different (and subjective) perceptions of what constitutes cruelty, and these perceptions can vary over time. Someone may find no cruelty at all in raising animals for food if they're well treated by the farmer, but consider that factory farming crosses the line. The same person, once becoming vegetarian or deciding to avoid consuming factory farmed animals, may develop/regain a higher sensitivity about killing or harming animals, out of being more exposed to information (through friends and social networking) about the subject than they had been previously.