Wedding rings are emotive things, people who put on a wedding ring are intending that that they will wear that ring from the day they marry until the end of their, or their partners’ life. Therefore the choice of ring, or rings if you both intend to wear one, becomes particularly important.
Palladium is actually from the same family of metals as Platinum with very similar characteristics. It’s hard wearing, though not quite as hard wearing as its brother metal. It does not tarnish because it does not react with oxygen and it has been recognised as a precious metal since 2010
The major reason is costs. All those High Street names need shops, staff, stock, security, advertising, corporate offices to name but a few need to be paid for by someone. They are paid for by you, the customer, in the large margins they have to put on the rings etc. that you buy.