I suppose it has something to do with them not being original to the gun, will they affect the "feel" of the gun adversely, the unsightliness of a poorly done job.
Remember that the "feel" (I assume you mean handling dynamics) of an old Brit gun is unlikely to be OE due to "aggresive" barrel maintance/honing. Soooo, sleeving gives the (new) owner an opportunity to adjust the gun's handling dynamics in the direction he desires via barrel length and wall thickness profile.
" --- the unsightliness of a poorly done job." A matter of willingness to pay for good work; an unwillingness to pay for bottom feeder work while hoping the "craftsman" will, by some miracle, gift you a first class job.
Remember the poem, "The Wonderful One Hoss Shay?" Well it applies to guns as well, perfect logic sure as he%%!
http://holyjoe.org/poetry/holmes1.htmDDA
