I made a point of never entertaining any children including my own. I provided the wherewithal and that included a computer, games, and TV and art materials, lego, blocks, books by the thousand, craft kits, board games, bikes, skates, bats, balls, mitts, dolls, dollhouses, doll clothes, etc (lots of 'etc'). They chose what they would do. I still have most of the gorgeous beaded hair accessories DD1 made, and I wear them. I also have huge files of the artwork they all produced as well as the Boy Scout crafts DS made. And we still regale one another with chunks of Simpsons dialogue. Also the songs and plots of various children's programmes we all watched together when morning sickness made forays into the kitchen or outdoors into the small of exhaust fumes horrible.
Their outdoor options were limited in summer to the pool or the garden sprinkler thanks to the way the sun heated up the local playground equipment and because it's not fun to run around playing ballgames or even riding a bike or skating when it's unbearably humid and in the 90sF. You can't keep small children out in heat like that. In winter the playground wasn't much fun either because of serious cold, and biking and skating were out because of ice and snow and cold, and dark afternoons. Skating at the rink was expensive for a session for the number of DCs I had to pay for.
So yes, the TV and the computer are both cheap and handy and if you're paying for the heat or the AC anyway you might as well get the benefit of them. But they can also be enjoyed together and are not necessarily a matter of leaving the children to it on their own, nor are they necessarily more harmful than providing books and letting them read for hours during which they do not get exercise or interact with others.
Actually, since screen time is often shared by children, there is often more interaction between them than if someone is reading. There is a good deal of regulation of behaviour of the kind interactive play requires -- they establish rules such as no standing in front of the screen, no annoying tapping or humming or other noises, no asking questions constantly by people who can't follow the plot, no demanding a change of channel if everyone else is happy with what's on, etc. So there are social skills involved in TV watching, and also in everyone using an X Box or game console. The Wii is especially good for interactive play.