What's the point of doing (ETS/ATS) World of Trucks External Contracts?

ets2 and ats have these world of trucks (wot) external contracts that become available when you connect your game to the wot system.

what is the point of these external contracts?

3 Answers

There are three points I'm aware of:

Fulfilled external contracts show up in your public profile on WoT, which is basically just statistics.
You earn achievements for the external contracts.
Every now and then SCS runs Community Events that require you to fulfill external contracts (in this case, the Operation Big Sur requires that you complete at least 15 deliveries from or to the construction site on Route 1 in American Truck simulator). Please note that Community events are optional.

"World of Trucks is envisioned as an optional layer created alongside the existing single player game." - SCS Software
Source: (very early Q & A).

Additionally to the things pointed out by Gerald, a few other things are,

"Special events" on World of Trucks only work with WoT contracts (e.g. During Christmas 2016, you could deliver giant gift boxes on trailers for unique paintjobs and other accessories).
There are no important or urgent (Just in time category) deliveries.
There's no deadline or estimated delivery time, you can't be late (for the same reason as above: this feature was dropped due to feedback received, as the always running World of Trucks service advancing time, while your shut off game would not).
WoT contracts will be suspended if the service goes offline (e.g. for maintenance), and can be continued at a later time without penalty.
Accepting a contract will drop the trailer for pickup immediately, you don't have to stop at the entrance of a company's place anymore (very convenient).
Not all kinds of cargo are available as in the regular freight market.
Although trailer types and skin might change with mods, only vanilla cargo types will be available through WoT.
Cities added by map mods will also not have WoT contract available, only vanilla cities.
The "trailer browser" also seems to be unavailable.

A few more points not covered by other answers (possibly because of changes since then):

Deadlines in real-world time, not in-game time: World of Trucks contracts have deadlines in real-world time, not game time. This could sometimes result in a more relaxed experience, where you can take small detours or rest whenever you want, for example to avoid driving at night in in-game time.
A much larger pool of jobs from a specific city: With freight contracts, you need to drive to wherever the job's origin is, and in smaller cities, there may not be many well paying jobs available. However, even in such cities, there are usually several World of Trucks jobs available that pay well, so this avoids the issue of accepting a low paying job or driving elsewhere to get a higher paying job.