Old thinkpad can be bought for a hundred bucks and upgraded with a 1TB SSD. Battery acts like a UPS and probably performs better and cheaper than raspi. As for why you should do it, you should do it so you can get privacy benefits using your node with Sparrow wallet to verify you own what you think you own and also to help make informed fee decisions running your own mempool instance. Eventually you should also have your own soverign lightning node connected to Zeus so you become your own bank and your own payments processor.