Sending a thank you email after an interview is such a bad habit we have made during interviewing
After every interview people are expected to send a thank you email.
My company encourages this behaviour. Coz they think that employee has manners or some rubbish. I dont see the point.

I usually write back with a thanks and add on open ended questions asking if I could have answered any questions better. Most do respond and it can be a good way to improve for future interviews.
As someone who has worked in HR. I understand your pain. I have seen so many thank you mails from candidates we know weren't going to get the job. Honestly after so many emails we stop noticing who's sent and who's not.
What is wrong with sending one sentence "It was pleasant talking to you. Thank you for the opportunity."
I think it's a courtesy to thank the interviewer after the interview. Above that it serves no purpose.
Being courteous can go a long way, since they might refer you for future jobs at the same company, but that's a very rare occurrence if you haven't already got the job in the first attempt.