Acquiring an experience certificate from a company or organization you've worked in is very important because it is the only standing proof or key to apply for new jobs.
Different Company Policies
Different companies have different sets of norms practiced for issuing a relieving letter or experience certificate. From the post above, it is not mentioned which company you are referring to.
In some companies, they have clauses included in their HR policies that deprive the leaving employee of an experience certificate, relieving letter, and even the last pay if the employee has failed to serve the notice period. Some firms don't issue an experience certificate if the employee hasn't worked for a specific time, as stated in the policy. For example, a company may deprive an employee of their experience certificate if they haven't worked for 5 years with the firm.
Legal Considerations
However, we can't blame the company for not furnishing the experience certificate since everything has to happen as per the clause in the appointment letter. But bonded labor is illegal, and an Indian citizen has all fundamental rights to employment and to make a livelihood as per their wish.
If you are in dire need of an experience certificate, I recommend you pursue legal action. It depends on how strong your stance is according to civil laws written in the Indian Constitution. It is better to seek advice from a lawyer if you intend to pursue the matter legally.
Best wishes