Why Xbox Game Pass Is Not Available In Pakistan?

Because you're located in a region where Game Pass is not available. EA Games like FIFA and Battlefield aren't available in Game Pass itself, but are available through EA Play which is giving by having Ultimate. If EA Play isn't available in Pakistan, that would be why you're not getting those games.

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This can be to a lot of reasons (marketing, viability, government, legal, etc)
Unfortunately no one here can tell you why your region is not supported yet

For now the best option is keep waiting

Pakistan is not a supported region so Game Pass is not available there and you would not be able to purchase it.

Pakistan is not supported by Live and Game Pass is not available there. So it's defaulting to a region where it is supported. https://www.xbox.com/regions

Use of a VPN is not allowed in the Rewards program and can result in a ban from the program. And since Game Pass Ultimate is not available in Pakistan, you wouldn't be able to use it anyway.