In parts of the world transit is run as a service instead of as a business. Here because it's a business if something (example: CRU's on platforms) doesn't make money it doesn't stick around
In parts of the world, transit is run as a business rather than a service. Here, because it's a service, there's no incentive to develop and intensify the land use and therefore potential customer base at station areas, since the land value goes to the private sector.
Is cost the only consideration though? My experience in this area is really only travelling outside of North America, but my favorite transit systems all have businesses and washrooms integrated into the transit hubs. Until we start to look at more of this, we're admitting that we really only care about cars.
Washrooms and businesses seem like they are two sides of the same coin since they're both amenities to transit users, but they work very differently. The decision to provide washrooms (or other public amenities like bike parking, heated seating, etc.) is based on political will; partially this is the will to spend on transit stations. But partially we have a mentality of hostile architecture, making transit stations less desirable to spend time in because we don't want "undesirables" spending time there; addressing this is much tougher -- it requires working on the root causes of addiction, homelessness, etc. and also a commitment to making better places, which requires working with all levels of government.
Businesses on the other hand require customers to survive. I suppose we could pay Starbucks to sell coffee; they'd be happy to take our money, but that's not really a good use of money (especially compared to the above). I don't know what your favourite transit systems (and hubs) are; I've been to some pretty nice ones myself, but I've mostly seen three typologies of retail in transit:
1).
Commuter / inter-city rail hubs. (e.g. GCT (NY), Victoria/Waterloo/King's Cross (London); Atocha (Madrid); Sants (Barcelona); a lot of Union Stations and Hbfs.). These can support businesses because not only is there a ton of traffic, but it's users of less frequent, and longer trains. If you have 45 minutes to transfer trains and then your next train is two hours to another city, going to a restaurant or buying a book makes more sense than if your next train is in 7 minutes and you'll be on it for 18 minutes.
2).
Shops in transit concourses. (e.g Tsim Sha Tsui HK; People's Square Shanghai). True shops that are in station concourses and corridors. These work because of the very high volume of foot traffic; the HK transit organization has done a ton of work in using their stop locations to build densely (and dense by world standards), and there's enough foot traffic here that even if one in a thousand people stop, that could still be hundreds of customers a day. This is a very different proposition from what we have here where if one in a thousand people stop you'd be lucky to have twenty customers.
Our typical design of surrounding a station first with stairs and passageways and then with parking means that there's also no population in the immediate station area to shop there. If there was a Starbucks in the Bridgeland LRT station, and you lived at the SE corner of McDougall Road and 9 St, you wouldn't need to cross the street to get to the Starbucks in the station -- but it would be closer to go to the one on 1st Ave because of the lengthy ramp and street crossing. At Brentwood, the closest apartment building to the station is a 320m walk from the actual station head, once you go up the ramp and across Crowchild.
3).
Transit / shopping interfaces. (e.g. Powell St / Westfield San Francisco; VCC and Granville / Pacific Centre Vancouver; Metrotown Burnaby; Dundas / Eaton Centre Toronto; 3rd St SW / The Core Calgary; Carlos Gardel / Abasto de Buenos Aires). Here there's a mall in a central location and the transit connects to the mall. The transit system helps the mall, but the mall would probably exist without the transit stop. Note that Calgary has this with the Core. Here, the solution isn't to build businesses in the station, it's to incentivize better connections to the malls. Unfortunately, Chinook and Anderson are both on the wrong side of Macleod to connect (although the Chinook connection has improved). Sunridge could have done better; they expanded in the 2000s but in a direction away from the station; ideally, they could have done the opposite and you could walk from the station head straight across a ped bridge into the mall.
If you have some other examples I'm unaware of, I'd love to hear them!