The visible light from a light bulb escaping the house is a very small amount of energy. If it's an incandescent, then it likely loses a lot of infrared radiation, the primary product of an incandescent bulb, out the window as well (although this would be mitigated by IR-reflecting glass commonly found in the last 20 years). If it's a fluorescent or LED though, there's almost no infrared radiation by comparison and very little energy is thrown out the window. Nearly all the heat they generate is inside the base and carried away mostly by convection, partly by conduction, and a little by radiation.

So yes, we can use items as minor home heaters. I'm literally doing that right now at my new place by leaving the incandescents in place to help a 30 year old hvac system. There are pools and office sout there being heated by bitcoin mining farms. But what about in 3 months when I need to cool the house? Suddenly, the charitable heating of wasteful appliances stops making sense. I stand by what I said: if a light bulb gets dinged for losing energy out the window, a computer gets dinged for <100% efficiency on its primary purpose.