Hiring is a pretty difficult task from the startup perspective as well as corporate ones too.

Why all the companies asks everything to a specific candidate?

Because they want to re-ensure you are the sharpest person in the process and can take on anything .. i.e. solve any problems.

Secondly people do not care about your personal background in the hiring process cause in startups and small companies hiring process is not well defined and no dedicated personalities for them, they are just normal people given an extra burden. Even in large companies even they spent very high on recruiting expenses but they have set an extremely high bar .. Such as they need people who can do on the field as well as do in theory .. Cause they need winners in all aspects .. this is common philosophy .. every damn persons who are misfits doesn’t fit any other company created a great company of his own ..

Finally Its not true that if you are not getting a job you should a start a company, rather you should try to doing independent consultancy or freelance work cause building a Company is sometimes the toughest job ..and building a great company takes your whole life .. Sometimes it takes much more hard path than interviewing in these large corporates or small cool startups.. Think about the other side too..

Good luck with whatever you will be doing in future ..