I have been removing the leafy branches from my tomato plants. Is that wrong?
There are branches and then there are suckers. Most people remove suckers (the growth occurring in the angle between the main trunk and stem) so that this maximizes fruit production at the top of the plant. If the lower suckers are left untouched, then fruit can form on these low suckers and bend the branches so that the fruit and branch ends up on the ground, and can rot.
Suckers are also removed differently depending upon whether you have a determinate or indeterminate tomato plant.
To properly prune a determinate tomato, pinch all suckers from the ground level to the first flower cluster.
To properly prune an indeterminate tomato, prune all suckers from the ground level up to the second flower cluster.
The effect of removing the lower suckers is to increase the air flow through the plant and discourage insects and disease. If other branches are not looking healthy, you can also remove these. Removing healthy branches for no other reasons can reduce the size of your fruit.