I've often heard it mentioned that if you are playing live and you have an edge on the table, then you should encourage there to be a straddle for all players, (obviously only straddling yourself is -EV).

Now presumably this is because if the whole table straddles, if you are a good player you can win more money than you otherwise would if no one straddled.

However doesn't straddling just reduce the SPR in all spots and decrease the amount of post-flop play, therefore decreasing the skill edge between players?

For example, if you stack a bad player that holds a marginal hand on the flop, he is making more of a mistake when the flop SPR is large right?

Is it because you effectively double the value of the 'BB', but your win rate will fall by less than half so that overall you are up $$ even if you are down in bb/100?

Everyone straddle = average pot is bigger
Similar edge over more money = more profit

This is somewhat accurate, but also there's diminishing returns with edge over stack depth. Live you often get to very deep stack depths, and reducing the effective stack from 200bb to 100straddles is not a significant reduction in edge.