And, granted, there's no command to commemorate the birth, death, or resurrection of Christ, but the way we do those things is through ordinary worship - gathering together as the people of God to sing, pray, receive his Word, and observe the sacraments. Wonderful! But on Ash Wednesday, folks get together to do those things and smear ash on their foreheads. Jesus gave his church two beautiful gospel pictures - baptism and the Lord's Supper. Ash Wednesday adds a 3rd picture not ordained by Jesus or commanded by God. Adding things not prescribed by Scripture to worship is not wise.
I believe it is (as many observers of Ash Wednesday and the Lent season it kicks off point out) beneficial to think on our sin and our need for repentance; to actually repent. I believe that prayer and fasting are a good way to do this (though as I noted in a post several years ago, what typically happens in Lent is not really fasting). I believe that meditating on our sinfulness and need is helpful preparation for truly appreciating the resurrection of Jesus. But I also believe that Jesus himself gave us the perfect way to do that. It is by remembering his finished work in our observance of the Lord's Supper. Here we remember and have our faith fed by what He has done. Ash Wednesday and Lent dangerously try to reproduce in our lives what Jesus went through in 40 days in the wilderness which tends to emphasize what we do. Dear friends, Jesus underwent that experience in the wilderness so I don't have to! He earned acceptance with the Father because I never could.
The reasons some of my evangelical acquaintances give for observing Ash Wednesday and Lent, I understand and agree with. The method by which they seek to accomplish those ends, I do not agree with. A Good Friday service observing the Lord's Supper would be a far better, Christ-centered way to prepare for Resurrection Day.