That's not how this works. You can comparatively easily scale up art departments, but you can not do the same with engineering and design. It's also much less difficult to find competent artists in their respective niches than programmers and designers. Art skills can be far more easily taught and to a wider variety of people regardless of their inherent talent than software engineering and game design at the required level. Especially in the area of software engineering, game studios also have to compete with other fields with inherently better work/life balance, which is far less so the case with e.g. texture artists, modelers and animators.

Art can also be produced sequentially in large numbers and making more of it at a certain high enough level of quality makes a game appear more valuable to consumers. It's practically guaranteed: Spend more on art, have more stuff you can impress people with, a more enticing value proposition. You can spend a fortune on game design and programming, but that's invisible and there is far less of a guarantee that it'll work out in the end (see: the phenomenon referred to as development hell), let alone attract customers.

Try marketing a game on mechanics and design instead of graphics. Most people pay maybe 15 to 30 seconds of attention to promotional material at best before making a purchasing decision. The vast majority of gamers do not read reviews, let alone whining essays about how some journalist doesn't care about graphics (which have been written since the 1980s - there's nothing new under the Sun). You can wow customers with fancy trailers and gorgeous screenshots, but you can not explain why your game that you spent 100 million on game design alone on has better game design than that blockbuster with individually modeled and animated facial hair.