A lot of people like backpack.tf because it's where you go to sell your for items pure instantly which can turn into real cash from selling keys to steam market(another player)
Marketplace I find is just another reference for backpack or guideline/trade history. (Homework basically)
Scrap.tf takes patience to sell your items and a lot of people don't have that.
I disagree with the trading convenience because there's paint bidders/items can be overpriced. You have to be MEGA careful when selling your items.
Scrap.tf is really great for raffles and BIDDING on auctions because sometimes you can get a good deal or swap your items for another item. Strongly recommend coming here if you have strong patience and browse for deals, teaches you the basics about doing research and trading. Strongly won't recommend selling your own items due to item value scammers.
If you're talking about trading convenience as it's done by a bot and you can set your IF(overpay) level to w/e you want then sure, convenience is the right word.
And I'm pretty sure the bot says "don't use me as a bank"