Because they think you can…
Because they think you can throw them in a tiny cage and expect them to thrive. People don’t understand that budgerigars are just as expensive as any other small parrot. They need interaction and exercise. It’s time consuming to take care of them properly.
They’re a commitment, and should be treated like a companion, not a centerpiece. I certainly would never call any bird an “easy pet.” Not if you’re caring for them correctly! It takes a great deal of time and patience to provide the correct food, toys, and mental stimulation a bird requires.

I would instead call budgies a good “starter bird.” A good way to evaluate whether or not having a larger pet bird is for you, or if you want to stick with the smaller ones. Remember Females, or older birds that were not hand raised will be more difficult. Learning how to tame and handle your budgie takes time and research.