Why do colleges like Lovely Professional University, Sharda University, and Amity University advertise on TV? Do these universities have any standing or credibility?

No, these universities almost have zero credibility. You have to realize the fact that the main goal of these big universities is to make money. 

I have heard a lot of reviews from my friends who studied at these universities. Following are lesser-known facts about these universities:

• During the admission, you will be told about the institute and will be assured about top-class facilities including AC in your classrooms. When you get allured in, you will face reality. Your expectations will be barely met. 
• Most of the teaching faculties are newly appointed with most of them having no experience in teaching at all. Most of them will vanish after that semester and again, new faculties are appointed. 
• Attendance criteria is very strict and teachers' way to control students. Even if you are five minutes late to the class, talking in class, or unable to answer a question in class, you are marked absent. 
• There is no particular format for allotting the internal assessment or Semester end exam marks. If teachers are not that fond of you, you are definitely going to have a tough time here.
• Making students reappear in their exams is a new scheme of making money for these institutes. Whenever the results are out, around 80% of the class is going to fail in one or more papers. To reappear for one paper, you have to pay 5-8K.
• Fee demand is very high and ROI is very low, due to which the number of students drop out every year. 
• You will be judged in every aspect, based on what you are wearing, that too if you are a girl. You will be sent back to hostels.

Overall it's a no-brainer to avoid attending these institutes. Paying so much when you are getting so little in return, makes literally no sense at all. So think twice before opting for any of these institutes.