I think many folks misunderstand or are confused by the terminology when it comes to tippets & leaders. Every fly "leader" has a "tippet", which is simply the end that attaches to the fly. Tapered leaders have one end diameter larger than the other which would be the butt end. Straight leaders being simply a straight section of line, would still have a butt end & a tippet end. However that would only be determined after the leader is attached to the fly line. The tippet end is always the end that you tie your fly to.
If you're buying ready made leaders, whether they be knotless or knotted, there's usually a section about 15" to 18" on most that's included that would be considered the "tippet". That's not to say you have to add any additional "tippet material" in order to tie your fly to it. You could if you so choose, or if you need a longer leader.
I make most of my own now, but used to just buy the knotless tapered leaders, and tied direct to the small end which is the tippet end. As that end gets cut back by changing flies I would add about 18" of tippet. The only real issue with not adding more material you might encounter would be when using small size hooks, as the leader material may be too big in diameter to fit thru the hook eye. Otherwise, do what works for you. There are other considerations too for adding more material, such as drag or to get the fly further away from the line as line slap on the water can be a problem with some types of fishing. If you're attempting to fish with tiny dry flies & only have a 3' section of your leader left, then that might be a good reason to add something longer & smaller diameter. If you're casting streamers or bug bass bugs, that 3' may be perfectly fine. This is why leaders & tippets are made & sold in many length & diameter configurations.
For some fishing I do with sinking lines & big flies I'm using a straight section of 20 lb test mono of about 2' to 5' long, which is basically what you're doing after you've cut back the smaller end of your leader.
So to answer your question, yes, sometimes I do!