You can configure multicast between spokes with command ip nhrp map multicast <remote-spoke-outside-ip (nbma)>.
As @Steven wrote, it's not practical for a several of reasons.
For a full-mesh design, you need to static configure this command on every spoke, and one of the advantage with dmvpn and nhrp is that spoke can have dynamic ip address on the wan interface. So with "map multicast"-command you need to update all spokes everytime a spoke changes an IP address.
With a fulll-mesh spoke-to-spoke design with active ipsec tunnels between all spokes could be an hardware issue (depending of how many spokes etc...) So to be sure for that to work you might have high-end hardware on all spoke sites.
Thank you for this info! What I am rying to understand is "why" it is not possible, since the encapsulation is the same (spoke-hub or spoke-spoke). So I´d wonder to understand in details the reason why the traffic should go through the Hub.
have a look on the link above