think of the common calibers that people reload. 380, 9mm, 38 spl, 357 mag, 40 short&weak etc etc they all use SPP.
45acp is the only one in my opinion thats reloaded as much as any of the above and then you have 44 mag, 44spl and 45lc that arent nearly as common, all of which require a lpp.
im sure spp have 5x the demand as lpp do.
that being said, starting low and working up a load, you can use small rifle primers for the time being. they have a harder cup so they may not be 100% reliable in pistols with a weak firing pin hit, but I have been using them as of recently without problem.