There are three really practical reasons: First, the Jewish tradition holds that "the righteous of all nations have a place in the world to come," which is to say, you don't need to convert to Judaism to get into heaven or (in Christian terms) to be saved. Second, Judaism is genuinely difficult. Conversion to any branch of Judaism requires a long course of study, and being a Jew involves "bearing the yoke of the commandments." We're not talking of the Ten Commandments, we're talking about the 613 commandments found in the Torah. Third, Jews are subject to antisemitism. Until recently, under both Christian and Islamic law, converts were routinely executed. In the United States, after Warder Cresson converted to Judaism in 1848, he was declared insane -- he appealed and won, but that still demonstrates how recent and fragile the rights of converts are. Saudi Arabia still imposes the death penalty on Muslims who convert to other religions.
No Orthodox groups recognise Reform conversions.
Orthodox Jews rarely accept converts, but if they do, they require several years of intense study.
Orthodox Judaism follows the historical and traditional ritual beliefs of Judaism
No Jews, regardless of level of observation, seek converts. However, if people wish to convert, Orthodox Rabbis will assist them after being convinced that the potential converts are sincere in their actions. That being said, most Orthodox groups, especially Chassidim, try to get non-observant Jews more involved in Judaism.
Haredi Judaism
Nothing. Jews do not seek converts. If a person wishes to convert to Judaism, they are permitted to do so, but Judaism teaches that Judaism should not be proselytized.
Orthodox Judaism.
Orthodox.
Orthodox Judaism.
Yes, but Orthodox Judaism does not.
Orthodox Judaism is growing.
Hasidim are a portion of Orthodox Jews. They follow Judaism on a strictly Orthodox level.