It's all about the tax code.
Section 132(f) of the tax code allows employers to provide "qualified transportation fringes" that are excluded from the employees taxable income. These do not include bicycles but do include:
- A ride in a commuter highway vehicle between the employee's home and work place. The vehicle must seat at least 6 adults (excluding the driver) and the expectation must exist that at least 80% of the vehicle's mileage will be for transporting employees between home and work. Employees must occupy at least one-half of the seats, not including the driver.
- A transit pass. A pass for purposes of this exclusion is any mass transit pass, token, farecard, or voucher entitling a person to ride free or at a reduced rate on a mass transit system or in a commuter highway vehicle as defined previously
- Qualified parking. This is parking that the employer provides to employees on or near the employer's business premises. It also includes parking on or near the location from which employees commute to work using mass transit, commuter highway vehicles, carpools or any other means.
Periodically (annually?), there is an attempt to amend the tax code to add bicycling benefits. The current version is the "Bicycle Commuters Benefits Act of 2007" (S.858 & H.R.1498) that would add the following as a "qualified transportation fringe":
(F) BICYCLE COMMUTING ALLOWANCE- The term `bicycle commuting allowance' means an amount provided to an employee for transportation on a bicycle if such transportation is in connection with travel between the employee's residence and place of employment.See http://blumenauer.house.gov/issues/I...&SubIssueID=25 and http://thomas.loc.gov/cgi-bin/bdquery/z?d110:s.00858: or http://thomas.loc.gov/cgi-bin/bdquery/z?d110:HR01498: