Today the Yemeni Army (Ansarallah) shot down the 6th American Scan Eagle drone of the invading US-Saudi coalition of 2021.
Reason 2 doesn't apply as Syria got S-400 from RussiaPossible.
It's also possible they can't purchase long range SAM from the United States since that would upset their old enemy/neighbour to the East.
Likewise, they can't possibly purchase long range SAM from Russia for the same reason bearing in mind that many Israelis are actually immigrants from Russia. Even if such SAMs were purchased, expect Russians to compromise the system through backdoors installed.
In that regard, an indigenous solution would always be preferred. Egypt, much like Turkey, Pakistan, Saudi Arabia, India or Indonesia, seems to be lacking. Ideally Egyptians should try to go the Iranian route and develop their own domestic equivalent of the Bavar 373. There are obviously domestic constraints that does not allow such a pursuit that would be too tedious to summarise.
However, no foreign imported long range SAM can be as effective as a domestically developed one for almost all countries in almost all circumstances.
Egyptians operate the S-350VM for their land based air defence command.
Syria doesn't have s-400. Russia brought s-400 systems to its own military bases in Syria. Syria finally received old versions of the s-300 a few years ago, but there is even debate about whether Syria is allowed (by Russia) to operate those independently.Reason 2 doesn't apply as Syria got S-400 from Russia
You're right about America though, and it's the same reason why their airforce doesn't get advanced AAM missiles.