Taxes are high enough (especially on high income employees) that if the employer can count it as an expense, and it doesn't count as employee income, then it's worth providing as long as the employee would be willing pay ~60% of its cost from their post-tax income. Factor in bulk discounts and the figure is more like 50%.

Unfortunately, the debate on payroll/income taxation never really addresses such distortions, and gets stuck on "come on, an extra 10% isn't as big a deal for you".