The (jurisdictions will have their own phrasing) 'demand' placed upon lawyers is that they are competent at the work they're doing.

The magnitude of knowledge needed to push a company to become public or undergo a merger, to litigate a divorce with children in custody, to defend an individual in a murder trial, or to litigate an aboriginal rights claim is substantial and there is very little overlap between them.

The issue isn't the regulatory requirement for competence - it's that the fields of specialization require years to become decent in.