1) their presence is only requested by the most vile of midwit goyim. The most subhuman slave-like posters require IDs and flags so they can feel confident enough to engage in their sickening hubris and smugness. If they can't tell who is who and from where, they cannot shit out useless garbage at significant rates. The uncertainty reigns them in, it is the only thing that works.
2) being tied to your earlier posts in a thread, and to a country itself, leads to censorship. My stand-alone post may contain brilliant insights that are necessary to hear, but if it is contradicting my posts earlier in the thread, or even contradicting the expected attitudes of my country, the posts will be self-censored by the reader and the insights may be lost on them.
3) flags are useless unless every VPN and datacenter is blocked. Introducing flags inevitably leads to blocking all VPNs as the goyim start demanding ever more certainty so they can indulge in even more disgusting and worthless hubris.
Those are my top three reasons that flags and IDs are bad.