Why are yields on higher coupon bonds always higher than lower coupon bonds?

says in the notes (as part of anomoly switching section) that all else being equal yield will be higher on high coupon bonds so need to monitor the change in the difference in yields over time in considering a switch rather than which yield is higher - as lower coupon will always be higher.

Does this suggest that there is more demand (tax reasons maybe?) for lower coupon bonds or are higher coupon bonds viewed as more risky (although that wouldnt seem to fit if were Gilts?)

 

I think it is tax reasons: investors generally have to pay more tax on higher coupon gilts and bonds, because they generally have to pay more tax on investment income than on capital gains. The higher yields on higher coupon bonds compensate for this.