Even if you do have access, building a set of services in close proximity with each other - yet still working on separate containers or even containers on separate container hosts - still needs a single source of truth where time is concerned. This is especially important if you have time-based transactions with eventual consistency, yet the order of those hundreds to thousands of transactions per second need to be extremely reliable. Having all the parts work off a single known, trusted time server such that the timestamp of all transactions can be absolutely trusted is supremely critical in some applications.