Many adverts have famous songs that have been taken and their lyrics were changed to become a jingle. Is this lazy marketing? Why is it done?

It's riding on the tune that is already well known. That does tend to save a lot of money in awareness building and also tends to "stick" with the public. You can call it lazy, you can call it cheap and dirty or you can call it smart, all depends on case in question.

A hit song is recognized by multiple levels of society despite their demographic differences. the audience will be attracted to the song they love and will try to know more about the product, and so on.