Plus the Gov't in questions had huge surpluses of existing rifles (proven rifles) that with minimum mods could be updated.
I'd say that would be one of the main reasons. Many countries had vast arsenals left over from WWI, composing of rifles, machine guns, and other small arms. As the rest of the branches were modernizing (air force, navy, armoured corps, artilllery, etc), the infantry rifles were left by the wayside.
Just think of what changed the most between WWI and WWII: submarine warfare, ship warfare, tank warfare, aircraft warfare, and tactics. All of those require expensive development programs, and were obviously much more important to the war effort than 'just' rifles. The most modern infantry rifle in the world won't save your battleships from aircarft carriers or subs, or your infantry from modern armour, or your factories from tactical bombers.... All of those things require expensive programs and a good chunk of industrial labour output. Rifles got left by the wayside.
Don't forget, the Lee-Enfield, Mosin-Nagant, and the K-98 were ALL supplanted by cheaply made, more modern, sub-machine guns that acted as a stop-gap measure for the more frequent close-in fighting of WWII.
Skippy said:
Your country wasn't quite as devestated by the previous war and had the resources and manpower to undertake such an enterprise.
True, but the Russians, by contrast a very poor country, still developed the SVT 40.... it just wasn't well suited for their peasant army, but the PPSh sure was! The Americans, being a more industrialized society, took to more complicated weapon systems easier than the armies of 'old Europe' did.
As for the Germans, and French... they were too busy developing bigger weapons systems to kill each other with. The French had the Maginot line and a collection of geriatric Generals leftover from WWI who had their biases. Even fresh minds like DeGaulle encountered much resistance to his 'crazy new ideas' like combined arms tactics and independant mechanized divisions.
As for the Germans... they were too busy re-building their Navy, Army, and Air Force to worry about rifles. Hitler had his preference for the K-98 as well.
The Japanese suffered from much of the same issues as the rest of 'old Europe's' armies did: An indifferent, dated, officer corps, with the added hinderance of Japanese tradition. "If that's all we had when we joined... it's good enough for you" Samurai defended their honour like men, and not with such 'ghastly' weapons that gave the peasant soldiery so much individual power.
I really need to back off on the coffee.....