Couple possible reasons. Note that I don't have sources for these.. some of this is based on what's happened to bikes I've owned with both brake types, but I don't have long term data for the designs.
Service life. V Brakes require separate tensioned springs in the left side and right side of the brake. If one side's spring gets weaker with age, the spring on the other side pulls the whole brake out of alignment with the wheel. This forces you to tighten the spring on the weak side, which causes it to get weaker even faster, until you run out of adjustment room on the brake. When that happens, the whole brake needs to be replaced. (Speaking personally, the brake pads outlived the brake)
Traditional brakes use a single leaf spring, rather than two independently adjusted springs, to control the brake. This means that you never have a case where one side ends up being "stronger" than the other.
Next, mounting hardware. V Brakes require mounting lugs relatively low on the fork, or a separate piece of metal on which the actual brake arms are mounted. On most road bikes, carbon forks are used, which makes providing these mounting lugs difficult.
As for your road brakes, on most plain road brakes I've seen locking both wheels up is relatively easy to do in dry conditions, and plenty of stopping is possible in wet conditions. The only cases I've seen where you can't stop well is in oily conditions, and V Brakes don't handle those any better. (Disks are the only brake type that handles "oily" well)
If you're having issues stopping, consider that the brake handles have some affect on how much force you can apply to the brakes. Really short levers do better with V Brakes simply because V Brakes provide more leverage. However, you pay for that leverage with more cable travel. I've been told (though have not verified) that V Brakes can't be used with most road brake levers simply due to cable travel.