From a discussion today with someone who wishes to remain anonymous (emphasis mine):
I think you'll find most of these [network management tools] are sort of a RANCID outgrowth - config monitoring systems + other functions which differ between all the vendors, although there is growth towards an approach of establishing a baseline and then creating and enforcing compliance rules/templates across the network. I think we're a bit cautious of using software written by someone else that writes to a device (all of the [network management tools we were discussing] do, but those functions aren't widely used), opting instead for tell me what's different and I'll change it myself. As more of these tools become well known and stable, and with more people using automated provisioning tools which do network device writes, that attitude will gradually ease off. But I believe many people are a bit scared of auto-enforcing features when it comes to routers/switches/etc., and maybe that explains a bit of what's lacking in comparison to sysadmin tools.
I agree with this assessment, but personally, I'm more worried about somebody fat-fingering a manual configuration. Another concern is that the configurations just getting too complex to maintain manually, particularly things like packet filtering ACLs, BGP policy statements, and so forth. In a lot of ways, it's like the old arguments about programming in assembly language versus higher-level languages.