Just because.
Society for the Advancement of Linear Time (SALT)
The Society for the Advancement of Linear Time is the anti-time travel organization of its particular game world, very possibly because SALT is an easy acronym to remember. The first iteration of SALT existed under a different, less memorable name (the Chronodynamic Interdisciplinary Working Group), and was a collection of engineers and scientists thrown together during one iteration of the typical temporal chaos that always shows up after the ‘discovery’ of time travel. They were looking for a way to protect the timeline from being casually overwritten: they found it, and even managed to get it up and running. Somehow.
This is actually extremely rare — time travellers are excellent at wiping out stabilization efforts before they can even technically start — but an infinity of timelines implies an infinity of low-probability outcomes. In this universe, SALT’s created a ‘bubble’ around their True Present that protects against artificial changes of the past (and, technically, the future). It’s not perfect, but it does prevent the largest, most disruptive alterations to history, and mitigates heavily most of the other ones. As long as the Bubble exists, so does the SALT timeline.
SALT is organized as a private regulatory agency with an extremely broad agenda. It claims veto power over any and all acts of time travel; both the United Nations and the European Union recognize that claim. The USA, PRC, UK, and Russian Federation do not, but SALT has privileged relationships with all major nation-states. The group is largely funded by ‘licenses’ offered to official government time travel programs, which then in turn enjoy near-exclusive access to potentially profitable sections of history.
These relationships are widely criticized, but rarely actively opposed. Most people find the status quo acceptable — and SALT ruthlessly protects it with a combination of legal action, corporate espionage, and (very occasionally) mercenary work. It is absolutely ready to come down with a heavy hand on rogue time-traveling operations, and is generally not interested in trying to recruit them, first. There are applications online, if people are that interested.
SALT personnel self-select for fanaticism about protecting the timeline, to the point where there’s considerable internal discussion over whether time travel should be permitted at all. The primary reason why the group does allow time travel is simple: money. Without government funding, SALT can’t maintain the reality stabilizers for very long. And the government funding will dry up if nation-states aren’t allowed to travel through time at all. As it is, SALT is remarkably ascetic and thrifty, for a group with its level of power and influence.
The situation is such that some of SALT’s regional offices and personnel have been known to supplement local budgets via inappropriate means. For example: the past is an excellent place to hide illegal drugs until the heat is off. And if they’re brought back (or just dug up), then what’s the harm to the timeline? Particularly if every dime of the payoff goes to keeping the lights on. Eggs, omelets, greater good, and all that.