There's no excuse for this. There should be a watchdog group in the federal government, staffed with people who make .01% commission on every dollar of waste they find and eliminate on shit like this.
There are also various levels of auditors within the organisation, some of whose reports are used as inputs for the IG and GAO.
However, there are diminishing returns at some point. If you want to go after, let's say, the 99th percentile within which things like soap dispensers might fall, you may have to spend more in admin costs than you get back in savings.
This applies to both needing more staff and needing to add more paperwork, which also in turn can slow down projects.
This DoD IG report, for instance, faults the US Air Force for not having built a database that tracked historical prices and tracked equivalent COTS part prices on various commercial marketplaces. That means either having staff or (more usually) paying some third party contractor to maintain a database and constantly update it to track all of these commercially available products. At some level you can end up spending more than you save.
That's why in corporate audits there's always a threshold floor below which external auditors don't bother to check further. It's considered an acceptable risk.
Also, there's a human aspect here. Doubt any air force officer wants to be the one to approve a COTS replacement for something like this only to have something go wrong on a flight because of some or other unexpected failure.