Have you actually tried using it? Four problems:
1 - The bicycle belongs to your employer, and when it's ownership is formally transferred to you, you have to pay tax on it.
2 - The 'cycle Scheme' is implemented separately by each major bike shop running their own scheme, Halfords runs Cycle2Work, Evans runs Ride to work. Your employer signs up to one or the other. If you are on Cycle2Work you can't but from Halfords
3 - If you want something that's not in Halfords, like a specific seat you like or a Bafang Conversion kit, then you have to go to independent shops that are 'in network'. Halfords charges 15% commission, and Evans charges 10%
4 - Employers set random limits, for example my employer does not allow over 1K spend, so you can't buy a decent ebike
Most people would not even realise that there are little shops besides halfords on the scheme, and attempt DIY.
Basically I think it would be much simpler, and cheaper to administer if we did away with all the employer nonsence and just removed all taxes from bicycles, like VAT.
That's absolutely not correct, the tax subsidy for buying bikes and ebikes in this country is bonkers and better than pretty much anywhere else. If you have any job you can always buy any bike(including an ebike) through the cycle to work scheme meaning it's deducted from your salary pre-tax (meaning that effectively it's a deduction from your own income tax).