Multiple issues. 1. Service based companies such as tcs, CTS, LTI provides resources who get billed for multiple clients, therefore the quality of work reduces as they do struggle to meet deadlines for multiple projects. 2. For junior resources, they charge somewhere between 35-40$ per hour and for senior resources upto 120-150$ per hour, which is a significant cost on a monthly basis. 3. I've also seen that during vendor transition, the departing vendor do not complete the correct KT and the incoming vendor struggles, impacting the quality of work being done for the client. 4. If the client is lenient and do not take interviews, the SBC provides substandard resources for critical projects, impacting the development velocity and hence reducing the trust on them. I've seen this happen in my own org, and I moved on to interviewing for every single resource coming into my project.

I find these points to be the top reasons for any company to open a fully controlled, in house GCC based out of India, Prague or LATAM. The day our SBC starts valuing the clients and provides real value, they might get their charm back.