1. you need motors for wipers
1a. motors means unnecessary power draw and a loss of space for both the motors and the wiring ensuring they function
2. public rep. if we look stupid, we get treated worse by more established groups, like a weaker/shittier cape. admittedly it can have its advantages, people underestimating us, but we took out jack slash, so that's not happening even if we look stupid, we'll just get a worse reputation overall.
3. hydrophobic glass isn't even tinkertech, we have it in the modern day. i brought up colin being an ex-tinker due to the fact he might have thought of some barely tinkertech solution ages ago
4. in the situation you present, wipers would make less of a difference than hydrophobic glass anyways, due to the delayed wipe versus things just sliding off. and if you mean a torrential downpour so thick it'd be effectively mist, then the difference in pros is irrelevant entirely, so we would only care about downsides
(edited)