Many staff value an employer who helps them in ensuring that they have an income in retirement. While it will not always be the most important determinant, as workers get older and start looking towards retirement it could potentially be a key HR issue.
Conversely, now that employers are not able to forcibly retire workers solely on age grounds, you need to ask whether you are happy for your staff to continue working late into their 60s or even into their 70s? Staff are more likely to wish to retire at a point when they can afford it and a good workplace pension can assist in succession planning.
Given that compliance with the legislation is required, the more positively you sell the benefits to your workers, the more value they will put on you providing those benefits. If you provide them begrudgingly, you will still have the cost of the providing the benefits.