OK a gift is a gift and any bride would indeed be grateful for whatever something someone chose to give. But if you literally have all the material goods you need, you are doing your caring friends and relatives a favour by letting them know that towels/crockery etc etc etc would be a bit of a waste.
You are acknowledging that people want to give a gift while helping them choose something which will actually make a difference rather than throw money away. Not a lot different to a gift list at a department store then really is it!
Most of the poems, requests that gifts take the form of money say something along the lines of, we don't expect a gift, but if you want to give one we suggest this is what would make the most difference to us as a couple starting out on married life.
Often with an alternative small gift list for those who don't like giving cash.
I really don't see what is wrong in that. 
the tradition of household items etc as gifts stems from times when a couple married very young and moved into their first home on their wedding night. This rarely applies today, so a new culture of giving for the new norm of becoming a married couple makes perfect sense. Only a luddite would fail to se this IMO.
Surely the point of a gift is to impart well wishes and bestow a boon on the couple. It is not vulgar for this to be cash. It is odd to insist a gift must be tangible in order for it to be acceptable. Those gifts cost money, but will benefit the couple less than the money would.
Someone said vouchers for particular thing would be better. Money is the best voucher in the world. Some strange and arbitrary lines are being drawn, based on out-dated cultural norms.
The bride is being pragmatic and helpful to her guests.