As for why, it’s just a question of aesthetics. I think these quotation marks are unnecessary, and I’ve never seen a professionally edited sheet with quotations are the title, except perhaps pieces with unofficial nicknames, like Chopin’s Prelude op. 28 no. 15, which has been dubbed “Raindrop” by Bülow.
Well, I'm in no position to judge your taste in aesthetics; personally, I like the quotation marks. Some on here might say this specific format sets us apart from other sheet music archives, or maybe even say it's iconic in its own little way. But you
have set this up as a petition, so I guess that will come down to the opinion of the general census.
And I’m posting it now because I’m temporarily back from hiatus and I just happened to think of it.
Sorry, I didn't clarify; I meant that nearly
fifteen years into the site's lifespan seems too late to justify the effort involved in changing this (that is, if site-wide consistency was to be a priority). Yes, you argued that this would be like us changing the URL, but that was done because once the site's address was updated, this fix became necessary. Sure, people can still easily find the site regardless, but I'm not sure this was a fair comparison to make to an aesthetic change.
Right now, the site's focus is replacing old sheets
(some of which have no quotation marks) that no longer fit our standards of quality, and there are still many that need our attention. Will this replacement scheme become an endless cycle? Who knows, but my stance is that this change isn't as necessary as you make it out to be, and that we have more important matters to address.