Well, you aren't blasting many long tunnels then. I blast tunnels that are over 500 tiles long, to do that i need 167 sticks of dynamite. That is ~70 gunpowder to make one tunnel.
If i didn't cut holes then i would have to use 500 sticks of dynamite... See what i mean by waste?
As for diamond armor and diamond tools and diamond period. That would be fine and dandy if only one had lots of diamond to spare...
And i don't find much joy in manually killing mobs. The odd gunpowder i get from creepers is enough for about 64 sticks of dynamite to get myself started with blasting but the real source of gunpowder i get from redstone and coal dust recipe.