Player's Map of Chult

Question

Straight foward question. What makes the map players get at the beginning so special? It doesn't really make sense that the local Princes don't have maps they can sell.

Answer 1

It's a uniquely-good map.

Seriously, no other map of that quality exists. (The geography of Chult was rearranged during the Spellplague and its notoriously-difficult-to-navigate interior has not yet been widely re-explored and -mapped.) Here're some ways we know.

Syndra says so:

Mapping [Chult] has always been nigh impossible, and nothing is known about the region's current geography beyond a few miles from the coast. ("Starting the Adventure," p.8)

And so do others:

Lerek Dashlynd... offers to trade a sailing ship for an accurate map of Chult that shows the exact location of the ruins of Nangalore and Orolunga. ("Side Quests," p.17)

Because of his dealings with explorers, Jobal has an intense interest in maps of Chult. He would pay the characters handsomely for Syndra Silvane's map, if he learns of its existence. If they refuse to sell, he'll resort to theft, and eventually to murder. ("City Denizens," p.26)

[Valindra's] bookcases are filled with books, scrolls, tablets, and maps, all about Chult in one way or another. They cover history, geography, culture, and natural philosophy in great depth, but all of them predate the Spellplague. Valindra would literally kill to possess Syndra Silvane's map, if she learns of its existence. ("Heart of Ubtao," p.60)

Answer 2

Page 9 of ToA, Under the Player's Map of Chult:

At this point, give the players a copy of Syndra Silvane's incomplete map of Chult.

I haven't read the whole thing but if this Syndra person had to use an incomplete map it's safe to assume a complete Chult map is not easy to come by if they exist at all. I don't know the background of the Chult, maybe it's too dangerous to travel and map the whole thing.

In case you are asking because the adventurers lost the map during a session you can simply increase the navigation DC (or give them disadvantage) to figure out which way they are going without a map and follow the failed check rules as stated on pages 37 and 38.

Answer 3

A lot has changed in Chult since the Spellplague (roughly 105 years before "present day" for most campaigns): entire cities have literally and figuratively vanished, new things have sprung up, others have moved. (As numerous sources point out, such as The Sword Coast Adventurer's Guide, actual geography has changed.) It's difficult to map thick jungle, in a land full of both ground-based and airborne deadly creatures; and so, most pre-Spellplague references are out-of-date.

The implication is that Syndra and her backers have access to a great deal of resources and rare modern information; this could be the first time since the Spellplague that somebody has taken sufficient interest to survey what they could and collect modern information on one map.

Given the unique economy of Port Nyanzaru, maps could be seen as the domain of the merchant prince with a monopoly on guides... why cannibalize your own business by selling a map that someone could copy, when you can make every new treasure hunter hire a guide (and give you a cut)? The information that people have is now, probably, a valuable and closely-guarded secret. Guides aren't going to jeopardize their livelihood by giving it away.

Answer 4

The best reason for players to not have a complete map of Chult is that this would greatly hamper their ability to get lost while exploring the jungle. When the DM tells the players that they don't know where they are, the blank spaces on the map will help them stay in character and not metagame.