Actually if you resign you are not entitled to termination and lay-off benefits as provided in Regulation 4(3) of the Employment(Termination and Layoff Benefits)Regulations 1980 as quoted below. If what you said was true, your company might have made a mistake by paying termination and layoff benefits to employees who resigned.
"4. (1) Subject to paragraphs (2), (3) and (4), an employee shall be entitled to termination benefits payment where his contract of service is terminated for any reason whatsoever otherwise than -
(a) by the employer, upon the employee attaining the age of retirement if the contract of service contains a stipulation in that behalf; or
(b) by the employer, on the grounds of misconduct inconsistent with the fulfilment of the express or implied condition of his service, after due inquiry, or
(c) voluntarily by the employee, other than under section 13 (2) or the reasons specified in section 14 (3) of the Act. .."
For details of the Regulations please go to http://pesaraonline.net/terminationbenefits.htm