Cutting hair and nails at night is prohibited since there was no electric current during those times

This assumption is utterly wrong. Let me explain. We cannot apply our own logic for every beliefs. If we read the Ayurveda and other scripture we can understand  that hair and nail is the byproduct of the Mala (waste) of the bones (asti dhatu)…one is not supposed to throw Mala anywhere or anytime they like after sunset ..after sunset negative forces will have more power ..that is why in puranas we see rakshas getting more powerful in war after sunset…so negative forces attract to you if you throw your Mala or body part  anywhere you like after sunset…this may be reason why one should not use the broomstick after sunset to clean the dust in home. Refer at 

https://www.banyanbotanicals.com/info/blog-banyan-vine/details/the-deeper-connections-of-the-hair/