Why do we lie during job interviews?

Let me start of by saying, I have been to 7 interview rounds in various companies from top Financial firms to technological firms, but am yet to translate my interviews into an offer letter.

I have found myself in situations where I have to lie about something I have not done in past. It's usually something that I have not come across in past and lying isn't easy, especially when it's a face to face job interview.

I am referring to behavioral questions that interviewers usually ask you to see how your thought process works and what you may do in such a situation. (a hypothetical one)

The problem is I haven't faced such a twisted situation in my life during my 3 years of work experience. My actions at workplace are reactions to what's going around and that comes from being sound and aware of your surroundings on office floor. I find below questions a little too much and I really hate the part when these questions are asked at every interview and the reality is quite opposite when you 'actually' work for that company.

I have never been in a situation where my manager told me that one of my colleague is going to be sacked from the job in coming days and as a result of him being fired soon, I will be given additional responsibilities with faith that I will execute them and somehow that colleague of mine comes to know that I know something about him that's not good. What will i do in such a situation?

I was truly amazed when a top financial firm at Wall St. asked me this and I was saying to myself Oh Lord! Why is the world so complex and does not go with the flow of the surroundings. Why do I have to fake my answer everytime when we never run into such hypothetical bizarre situations.

One other time I was asked, what factor will motivate you to leave your bed, get up and come work for us? Again, if I be true to my self, the answer would be because I earn money from your company to earn bread-butter for my family. But hey, they (HR) won't find this response upto their expectations. They are so engrossed into their fake worlds of imagination where they want to listen to some BS talk where the potential employee would say, Ohhh the work culture here is so amazing. I love the population diversity here and me being trilingual will give an edge in keeping floor engaged and more productive and blah blah...

Am I the only one who feel this way? and more importantly is it wrong for me to this way?

P.S: I am looking for Summer internships since Sept 2016 and after sitting for 7 interviews, I still don't have anything.