Andy Naselli has a great article with numerous quotes about why John Piper doesn’t own a tv. The article is long and well worth reading, here are a few of my favourite quotes from John Piper:
Turn off the television. It is not necessary for relevance. And it is a deadly place to rest the mind. Its pervasive banality, sexual innuendo, and God-ignoring values have no ennobling effects on the preacher’s soul. It kills the spirit. It drives God away. It quenches prayer. It blanks out the Bible. It cheapens the soul. It destroys spiritual power. It defiles almost everything. I have taught and preached for twenty years now and never owned a television. It is unnecessary for most of you, and it is spiritually deadly for all of you.
The startling truth is that, if you stumble over Melchizedek, it may be because you watch questionable TV programs. If you stumble over the doctrine of election, it may be because you still use some shady business practices. If you stumble over the God-centered work of Christ in the cross, it may be because you love money and spend too much and give too little. The pathway to maturity and to solid Biblical food is not first becoming an intelligent person, but becoming an obedient person. What you do with alcohol and sex and money and leisure and food and computer have more to do with your capacity for solid food than with where you go to school or what books you read.
Television is one of the greatest life-wasters of the modern age. And, of course, the Internet is running to catch up, and may have caught up. You can be more selective on the Internet, but you can also select worse things with only the Judge of the universe watching. TV still reigns as the great life-waster. The main problem with TV is not how much smut is available, though that is a problem. Just the ads are enough to sow fertile seeds of greed and lust, no matter what program you’re watching. The greater problem is banality. A mind fed daily on TV diminishes. Your mind was made to know and love God. Its facility for this great calling is ruined by excessive TV. The content is so trivial and so shallow that the capacity of the mind to think worthy thoughts withers, and the capacity of the heart to feel deep emotions shrivels. . . .