In this question, an interesting comment was added by @endolith:
If the route is listed in a guide book as a trad route, it would be seen as … very rude to install bolts on it
Is there a practical reason for not wanting any bolts on a trad route? I'm only familiar with sports/indoor climbing and generally speaking having lead bolts on a top rope route does not make it any more difficult to climb, even with carabiners already being in place. Is it different for trad vs. sports routes?
It’s not about making it more or less convenient. It’s simply about different styles and wanting to preserve the “original” style of climbing (trad in its current form isn’t really much like what the first ascensionists of the Victorian era did, but it’s the closest we’ll get).
Whilst it may be appropriate to bolt a route where there’s very little possibility of protecting it otherwise, once a route is bolted, there’s no going back and you immediately take some of the jeopardy out of it. Possibly you even take a bold and interesting route and make it mundane and pedestrian.
I love both sport and trad climbing, but they are different beasts. Sport climbing is about pushing grades, climbing hard and risking (and taking) falls. Trad climbing - whilst it can get hard - is for me more about the technical aspects; well placed protection, good rope work, problem solving, building belays and nice long multi-pitch days climbing mountains. And the leader must never fall!
There is, and always will be probably, conflict between the two schools. Sport climbers think trad climbers are mad to rely on flimsy wires and want to bolt everything. Trad climbers want to stop what they see as their routes getting ruined. As with all things, there is a compromise to be had.
(1) Rock climbing originated as a branch of mountaineering, and mountaineering isn't about modifying the mountain to make it easier to climb. If it's a trad route, then the first ascentionist was able to climb it without bolts, and that shows that it can be done.
(2) As a general principle, we don't create unnecessary impacts on the wilderness. This is the leave no trace philosophy. If somebody bolts a sport route, it's because they see it as a necessary impact, because otherwise the route would not be climbable (or safely climbable).
These reasons are the same, for example, as the reasons that we don't chip new holds in established routes in order to make them easier, or remove a bush that's in an inconvenient spot.
Since you ask for practical reasons, here's a couple:
Bolts are an unsightly intrusion in an otherwise relatively natural landscape. So they reduce the wilderness experience of climbing.
The presence of bolts will likely encourage a different kind of climber to the location, possibly in large numbers, who would not otherwise attempt the routes. This will also reduce the wilderness experience.
There may be other effects, but these are the main reasons I see for confining bolt routes to the few places they are considered acceptable.
(The question title asks how it makes the route "inconvenient" to climb, but I don't think that was ever claimed by anyone. On the contrary, making a route too convenient tends to make it less enjoyable, so I've addressed that.)
