I think the reason you see less of this is the core skills required are often very different. Architecture, vs interior design vs exhibit design vs installation art, product design, UX, branding, service design, etc.
You see a lot of companies who might have started in traditional ID or architecture and branched out over the years as some of their core work dried up. But other than the couple of industry giants most companies can’t maintain that diverse of a book of business to keep people across that many specialties employed.
You also see this type of business a lot where multiple offices exist in different markets and may focus on different core areas. IE a NY office might focus on ad/UX/brand work while a bay area office focuses on product or service design, etc. Most consulting groups evolve out of a couple of key clients which are often region specific. Teague probably wouldn’t be in business designing jet interiors if Boeing was located in Des Moines.