If you check Skoda and Audi configurator the Factory extended warranty is still avaible. The question is why has VW and Seat removed it.
Maybe a) the cost of warranty claims in years 4 and 5 exceeded the revenue received by VW from the sale of this option or b) VW sold very few of the extended factory warranty option, so perhaps they concluded there wasn’t the demand for it or c) if most people lease or PCP, they won’t keep their cars long enough to benefit from a factory warranty in years 4 and 5.
Could be any (or none) of the above. Maybe Skoda and Audi customer demographic is different to VW, which could be the reason for it still being available to those brands.
Anyone’s guess.