Why some muslim countries do allow israeli citizens to enter their countries?

The Islamic world isn't a monolith. They're allowed to have their own opinions on the manner, despite what other nations try to enforce.

To start out with, much of the Islamic world actually doesn't have any beef with Israel to begin with. They're just boycotting out of solidarity with the group that shares their religion, as they believed they "should". It's rather clear that some of the nations that are rather loud in speaking ill about Israel actually don't care too much internally, and are just doing it to look good to a few other states in the Islamic world who do. Much of this attitude is fading away, and increased interaction with Israelis in third-party nations and forums have lead others to believe that it's gotten ridiculous at this point. Israel is a part of their world and, honestly, I think a few realize that they're not the threat others may paint them to be.

There is great benefit to Israelis coming to their nations, I think. Morocco does allow in Israelis now but with relations more will risk the journey, so that tourism (especially from Israelis of Moroccan descent) would be something to desire. Israeli businesses are notoriously profitable in the West, and economically savvy UAE will clearly pay attention. And I remember reading about how Sudan may benefit from Israel's impressive environmental technologies. 

Edit: As for allowing non-Israelis but people who have been to Israel in, it's simple: They recognize they're NOT Israeli. A lot of those who ban those who have been to Israel in addition to Israelis are those who may have engaged in war with Israel (or still have active conflicts) but most who don't really are only banning Israel for the "Islamic solidarity" look. Some may recognize that people who go there may not have any dog in the conflict and it really won't benefit their country to just turn people away. 

Israeli citizens are poor guys, their government is Apartheid evil.

You should ask "why some Arab countries do allow Israelis to enter their countries" while the Apartheid state of Israel is ethnic cleansing Palestinian Arabs in their mother country.

COMMENT on Anonymous : stop making the smart, no diff between Muslims and Islamic countries, Saudi Arabia and Iran are Islamic states like the Zionist state is a Jewish state, all are crooked and theocracies.

Saudi theocracy are allowing  EL AL now to cross the air space of the kingdom.

Perhaps because it doesn't seem like a valid reason to ban them?

Why not?????????????????????????????

I don't know.  Are you trying to say that it's really NOT the religion of love and peace? 

There is a difference between an Islamic state and a country that is predominantly Muslim. Countries that are predominantly Muslim often will, while Islamic states never will. That's because Islamic states are theocracies, while countries that are merely predominantly Muslim are not.