Benefits are many though.
It is salary sacrifice, so is taken from gross pay. Your tax & NI contributions reduce slightly, as does the NI contributions made by the employer. Fitter & happier employees is also a good reason.
Are you public or private sector employed? Seems to me that private sector perhaps recognises the benefits more than public, the NHS Trust I work for took many years of persuasion before they signed up.
The scheme running within my employer is only open for a month in the spring, this has been carefully selected for three main reasons. People who are keen to join will wait until the next opportunity, those who don't consider themselves cyclists but wish to join the scheme are possibly more likely to be successful if they join in the spring, and there is less chance of someone joining in November or December & buying an all singing, all dancing MTB that they then subsequently "don't like" and palm off to teenage off-spring.