homepage – Entry Page for Multi-brand Website

I noticed that a lot of companies have a setup where the parent company has a site for each brand even though products may compliment each other.

For example, Fenty has multiple brands. There is Fenty (clothes), Fenty Skin (skin care), and Fenty Beauty (makeup). Each has their own website.

Duolingo has the learning site, podcast, and a few other tools. Each thing is on a different site or subdomain.

Would it be a bad practice to have an “entry page” to a site? For example – you go to the parent company site Cars.com and the first thing you see are links to go to cars.com/Honda, cars.com/Audi and cars.com/BMW. I noticed that some companies do this for site countries – you have to pick a country before “entering” the site. Would doing something similar for brands provide a bad user experience? Is there something that proves this sort of setup confuses users? Is that considered making the users do too much work to get what they want?

I’ve read a few things that indicate a setup like this could hurt SEO. So is the only reason this isn’t used as much for SEO?

It seems like a good idea to organize parent companies and brands, cut down on costs by having one site, and also let users know what other products you have (but they’re not forced to that part of the site if they’re not interested).