I agree with all the reason's offered above but have also been stockpiling figures for 30 years (by simply buying to many to paint), with a rationale that I will have lots to paint when I retire.
Much of my GA were state of the art when bought, but have now been overshadowed by better sculpts (a problem my brother also has with his AFV kits).
I have a Barton 90mm Mahnes, but then bought a 54mm Pegaso going cheap at a Euromilitaire to use in a vingette - then Metal Models brought another one out - all good models but am I likely to build them all? - not likely - the problem is which one(s) to hold on to.
Then there are the impulse and bargain purchases at shows which seemed a good idea at the time. I am a Napoleonic / Samurai nut but have been tempted by other periods, sci-fi and fantasy - these are unlikely to get built but you never know - "they will make a nice change!"
I have also only just finished conversing with Tubby-Nuts, over a request for an old Poste Militaire figure which made me question whether it was just gathering dust after all. Over the last three days I have changed my mind two or three times as to whether I really want to part with it , and yes, the impending Euromilitaire did encourage the idea of a sale to boost my budget a little.
Maybe I'm just in a fortunate place to have built up a massive grey army, but I know I'm not alone. Like a woman - it's a modeller's right to change his mind.
I now simply consider my hobby to be Model collecting - it's so much easier than doing all that painting - expensive, yes - but still fun - Ha-Ha!
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. Rubbish, yes you can. 
