Ask this same question to the Messianic Jew, or to MOST of the christian congregations in Israel, and you may be surprised. I was astonished at the number of "Messianics" who devoutly keep all of the feasts, as a form of ritualistic righteousness. The strongest of these, is Sabbath keeping, of course, but it is surely kept by Christians to the jot and tittle. It is plain Judiaizing, and in some places it is if there are two Christian Faiths, not one.
This has been taken to such extremes, that men like John Hagee actually believe in a Gentile messiah, and a Jewish one. I haven't figured out if there the same Jesus yet.
There is also a strong sentiment in Israel that magnetizes around a national identity, and an ensuing move to abolish or cripple other mechanisms that may continue dependence on any other culture. English is being minimized, as every Jew must learn Hebrew, and it is spoken less and less on a National scale.
The problem with keeping the holy days as ritual is that it doesn't necessarily have anything to do with the spirit of God, or operating out of faith, or obedience in the heart, nor does it have a whit to do with the actual cross that kills our inward Adam, so evil.
It certainly has the benefits of types and shadows, which may offer deep insights into the Kingdom and the ministry of our Lord Jesus, but is utterly impotent in it's ability to change a life to learn how to love.
By the way, the Pharissee's gloried in their obedience to the sabbath and the feasts. They murdered Jesus.