TBG isn't an overwatch clan remember? But that still has little to do with this unless your argument is that paid content means more activity from the clan vs free content.
If BF was free and they released maps in pairs, 2-4 maps a year roughly every 5-7 months, it would have a lot of interest especially with a one time cost that was normal game price. As we saw with lockers metro and others, a large portion didn't buy in to the xpacs from the start so loading up on xpacs maps vs just vanilla maps cut the available player base down. There are various reasons for that, but every xpacs would make a new tier of player and what's accessible to them.
Blizzard will make bank off of things like new skins, booster packs and other micro transactions that don't shift the balance of play. EA added the ability to buy extra packs, however they make no where near the kind of cash that blizzard does with microtransactions. As such, they package it up and ship it off as expansions which add to the total cost for a "polished/finished" game. Let's face it, it's a lot of money. It's a lot of pizza, a lot of tacos, a lot of McDoubles... that's gas for a few weeks depending what you drive.
If someone wants to buy a purple pimp suit for their BF character that's cool, but I'd rather get the maps and core game for one price and let their be frilly extras for others to buy so I can have a cheaper game. Hell, that's if the game runs like a polished game should from the box or if we have to go through weeks of tweaks and balances to have a stable playing experience. Some of the stuff they have churned out, the xpacs should be free for our troubles!