that is because you don't have many experience interviweing

other people.

If you do, you should know that there are so many resumes with impressive working experience, while the candidates know little about what they did. For example, a team gets a big project done. Definitely, any team member can put it in her/his resume. But how much he/she has done is another question.

Usually, interviewers will ask simple questions first. If you impress them from the beginning, the interviewers can directly jump into difficult questions, even issues in their current projects.

A side note. Programming is not hard, no matter it is OOP or procedural P. The hard part is an excellent OO design. One candidate can list all the design patterns in GOF book and it seems she/he really knows them. By asking some simply questions, however, you would know if she/he really understands them deep enough.

No offense. Just a little thought.

Of course, it is another story if the interviewer and the interviewee don't talk in one language. For example, it is a joke for a developer who can simply write some queries to interview a good DBA.