Initially people had fear that they will have severe side effects or might die but after they saw the initial phase vaccinated people are well, others also got encouragement. However due to that now there is a shortage of vaccines. Everyone wants their doses but Cowin portal doesn't have enough slots.
As I have said previously, it's like booking a railways tatkal ticket. There is no guarantee you will get one. If you get one, there is no confirmation you will vaccine will be available on the vaccination center.