Because they don’t believe in the Eucharist.
I happened to hear a Baptist minister on a local church broadcast this morning talking about the Sadducees. Of course, the standard Protestant thing is that that Sadducees were “sad, you see, because they didn’t believe in the Resurrection.” The problem is that they leave out *why* the Sadducees didn’t believe in the Resurrection (Scott Hahn and Marcus Grodi often talk about things that Protestants conveniently ignore): The Sadducees believed in Sola Scriptura. The Sadducees were the Fundamentalists of first century Judaism. They didn’t accept anything as God’s revelation except the Torah–specifically and literally. If a doctrine was not explicitly outlined in the five books of the Law of Moses, the Sadducees didn’t believe in it. They also insisted on using the Hebrew version of Scripture, rather than the Septuagint.
The Pharisees taught Scripture + Tradition, and they taught scriptural interpretation. That’s why Jesus spent more time arguing with Pharisees than He did with Sadducees–the Pharisees were worth arguing with, and we know at least some of them (Nicodemus, Joseph of Arimathea) agreed with Him.
Given that background knowledge, it is very funny to listen to Fundamentalist Christians criticize the Sadducees for teaching _sola Scriptura_ yet avoid the fact. The Sadducees didn’t believe in the Resurrection, angels, etc., because these things were not found in the Torah explicitly. They rejected Jesus’ teaching because Jesus was saying things that weren’t found in the written law. The Sadducees were the guys going up to Jesus and saying, “Where’s that in the Bible??”