In the old days, when surplus military rifles were cheap and new hunting rifles were expensive, it made a certain amount of sense. You could sporterize a military rifle for far less than the cost of a new Winchester.
Today, the cost gap has narrowed to the point where it's usually not economical to sporterize a surplus military rifle.
As a collector, I also cringe every time I see a hacked up relic. I have seen a few - very few - sporter jobs that were well done, but most I've seen appear to have been done by Bubba and his hacksaw. And Bubba's hacksaw doesn't know the difference between a 1942 Izhevsk (several million produced) and an 1893 Chatellerault (very few produced.) I've seen some very scarce rifles ruined by sporterizing.
Remember also, every time you chop up a cheap Mosin, that once upon a time 1903s and Lee-Enfields were plentiful and cheap. Now unmolested examples bring several hundred dollars or more and sportered examples are worth very little.
Putting aside my collector bias, when it comes to hunting I'd still rather have a nice old hunting rifle that was made for the purpose than a sporterized military rifle. My great-grandfather's Winchester 94, circa 1921, has been handed down to me, and it's still a fine deer rifle. But I like nice wood, blued steel, and iron sights. I have enough plastic in my life without putting it on a rifle.