We often read in ancient texts that someone cursed somebody else and something bad happened to that person. It is obvious that nowadays if somebody curses somebody else we really don't see any effect of that. Why did these work in the ancient past and why not now?
Curses are supposed to work even in Kali Yuga and currently we are going through Kali. The following verse from Parashara Smriti (verse 27, Chapter 1) is relevant here:
Krite Tatkaalikah saapah Tretaayaam Dasamirdinaih |
Dwapare Chaikamasena Kallou Sambatsarenatu ||
A curse in Krita takes effect immediately,in Treta it does so in 10 days time,in Dwapara after 1 month and in Kali it takes effect after 1 year.
So, we can't say that curses are no longer effective now. Moreover, it is difficult for us to verify whether a particular curse worked or not. And hence it is hard to find empirical evidence to prove that curses don't work now. Therefore, we have to go by what the scriptures say.