why are lawyers ao afraid to take on a big pharmacutical company or a doctor?

It may not be that the lawyer is "afraid" of the doctor. It may be that the lawyer does not believe he or she can find another doctor, in the same specialty and possibly in the same area, who is willing to say the doctor acted negligently. If one cannot prove negligence, one cannot win a medical malpractice case. In addition, you son must have suffered harm as a direct result of that negligence that he would not have otherwise suffered.

Lawyers will "take on" anyone from whom they believe will result in a big pay day.

You say the doctor did things "wrong." Well understand that the burden is on YOU to prove not only that, but that your son experienced harm that rises to the level of something compensible. If your son is doing OK, then there is nothing worth compensating. Sorry, but that is just how it works.

I've a had little dealings with lawyers...my advice is to hire the most expensive ones.

They are successful, or would have already gone out of business; but don't they have a ceiling limit?

There is also a LOT of $ to be made mostly for the lawyer against big pharmaceutical company, but that is only in a class action suit and they will fight tooth and nail, so to speak.

Perhaps, yours did "chicken out," and I'm sorry.