Why most companies don't care about employees without specialized certificates, while they appear to be costly for many employees with low rates?

One answer you might consider:  Specialized certification(s) for company staff might be a REQUIREMENT from the company's major clients.  For example, when a potential client makes a request for proposals to companies, it might be a condition of participation in the RFP that a certain % of staff (project managers, accountants, etc.) have particular certifications.  This can be especially true for large and bureaucratic clients -- such as governments, defense contractors,  petroleum industry.  

The thinking/logical here is that the clients are better able to compare proposals from various companies, knowing that a certain % of the company staff who will be working for the client have similar certifications across the various companies.  

It is important for the result to the employer and to reach the desired result should be on the staff to gain experience and competence through in-depth study in the area concerned