If I had to guess, it's probably people buying cheaper ingredients and/or not putting a whole lot of care into the process.
Having a poorly calibrated oven and / or overbaking can cause like half of these problems on its own. Substituting your oil / butter component (whether because of cost or for *health* reasons) can screw up a lot of baked goods. Lazy measuring of dry goods could do it.
I wouldn't say baking is *hard* but it requires an attention to detail a lot of people aren't prepared to give it.