Jungle Drums provides a decent attack speed increase to all towers in range for a fair price. It is especially useful where there are large groups of towers and/or towers that benefit most from attack speed increases. There is essentially never diminishing returns for a multiplicative attack speed buff, so its buff is still universal and can be used in most situations.
This upgrade is useful for the cheap attack speed increase that can be taken advantage of by all attacking towers. It is relatively inexpensive and has full buff uptime.
Jungle Drums can affect buffing Alchemists to make them buff more towers.
Uniquely, Jungle Drums has double the effect on Sentry Gun Engineers as it makes them build sentries faster as well as making them attack faster.