Use to do that, and it doesn't really counter the "pros" for a small capacity hand-pumped cleaner. That's why I built the DIY cleaner in the first place.
What happens if you want to clean some lines and all of your kegs have beer in them?
Cheers!
[aside: long day in the big city, I'll be glad to get home tomorrow!]
If all my kegs have beer in them, then all my taps are occupied. If not, then I have yet to NOT have an empty keg. I make it a point to always have at least one batch of kegs available at any point. That way, when the batch that's currently in primary is ready, it can be moved to keg. If a line needs to be cleaned, it's because it's just had a keg kick.
Also, since I ferment in adapted sanke kegs, which I always have at least one empty of, I have other ways of pushing cleaning and sanitizing solutions. Since I also use stainless QD's in my brew fridge, I don't remove them from the ends of the hose/line. Unlike the plastic QD's I have to use the nylon/plastic washer/spacer on these. SO, I'd either have to do more to clean the lines without a keg, or have something with a ball lock fitting on it to get the solution to run into. IMO, more work than just using the keg that JUST kicked. Since that one is now empty and needs to be cleaned, it's crazy simple to use it to also clean the lines. It also only uses a tiny amount of CO2 to do this. Since I have several CO2 sources (two for paintball gun tanks, one feeding the brew fridge and another carbonating beer in the basement) it's never an issue for me. The Leland regulator even has the hanging bracket on it, so it's easy to hang on the keg while using it.
For me, the additional hardware of a dedicated line cleaning setup is a waste of funds, time to build and more of a pain than using the keg that just kicked.
Use what you want to clean/sanitize the lines. Just know that there's at least two different (valid) ways to do this. Either use no additional hardware, or get/make a dedicated line cleaner.
BTW, where do you connect the line cleaner to? The ones I've seen require you to remove the faucet in order to clean the lines. With my method, you don't. Plus, you clean the faucets (internally) at the same time.