Why can't the police interrogate the suspect after the defense lawyer arrives?

Because it's not necessary.

The presence of a lawyer is not a necessary condition for the police to interrogate a criminal suspect. And generally the police will not allow lawyers to be present when interrogating suspects.

Explanation:

Don’t say anything unreasonable. It is different from foreign countries. This is determined by the current situation of our country.

The rule of law in foreign countries is relatively mature, and citizens have a high awareness of law-abiding. Lawyers and case handlers value their professional ethics and qualifications. Generally speaking, most people respect and fear the law. In the eyes of the public, the law is a weapon used to protect themselves.

But in the current environment in our country, people are not pursuing justice, but hoping to obtain favorable results through unfair means.

Therefore, the unfairness of some law enforcement officers (I dare not say how many) has caused the public to lose due trust and respect for the law and law enforcement officers. "Practicing lawyers" and "no professional qualifications" But the business competition of "manipulating relationships and monopolizing most of the legal business" also caused them to abandon their professional ethics. In the eyes of the public, the law is a machine for a few to make profits, rather than a weapon for the majority to protect themselves.

The result is: you don’t believe that the police won’t use torture to extract a confession, and the police don’t believe that the lawyer you hired won’t use secret tricks, such as secretly recording videos, suggesting that the suspect denies the facts, etc.