Rashi and Torah Temimah, from Yevamos 47a-b: If one comes to convert nowadays, we ask, why do you want to convert? Don't you know that Yisrael are depressed, pushed around, humbled and afflicted?! We inform him of the punishment of Mitzvos. We do not [frighten him] too much, nor are we so exacting with him - "va'Tere Ki Mis'ametzes