Random tables are a great way to create surprise and replay-ability in a module. They add variety to an otherwise linear experience. However, just looking around at some of the random tables for table top games like Dungeons and Dragons it's clear that random tables (both fan-made and official) require as much thought and careful design as any other aspect of a game.
One of the worst and one of the more common types of tables is the random adventure creator. The most obvious problem with them is that some combinations don't work out very well. It raises more questions than a setting or module may have answers for. Furthermore, we don't actually get a random adventure plot out of most of those tables, we get a loose summary of a scenario. The DM still needs to design things and do a lot of work to put things together. In short, the only thing the table generates is more work.
So that's where tables fail, but there are a lot of really good random tables out there. Notably the random tables in the video game Fallout 3 and the 5th Ed D&D module the Curse of Strahd (the dracula themed d&d module) have made some very good random tables. But why are they better?
Good tables tend to clue players in to interesting things and create the sense of a living world. When a random table is populated with elements of the world, it puts the DM in the driver seat. This does mean the DM needs to do more prep work but it also means that the prep-work will (likely) pay off.
Inward vs outward focus
An entire table and even its individual elements can be viewed as having an inward or outward focus. When a table focuses inwards, it tries to focus on the established world. When a table is focusing outward it creates questions that demand the expanding of the world to find an answer. While a certain type of balance is right for a good game, most table error on being too outwardly focused.
The inward focusing table or encounters explain or happen because of something that already exists or something that has happened. It leads player into things that have already been established or already been seen. These elements tend to ask questions that already have answers. There isn’t much of a mystery to them; it's more about seeing how things are connected.
When a table or encounter has outward focus it leads to something new. It requires new explanations and rationalizing for things to make sense. Often times, this may be the addition of something to the world. One of the major problems that most tables have is that they tend to ‘focus outward’ and that means rolling on the table often means that DMs have to expand their world. They have to try to explain a world where the rolls on the table would make sense. The problem is that this is just creating a world of ever more complicated explanations.
The inward focusing table is more about trying to show the world as a connected place. For instance, the players start running into goblins because there is a goblin cave for them to explore. The table creates encounters informed by your world building. Each random encounter is an introductory vignette that leads players to new perspectives or explanations of things in the setting. It invites players to think and explore the world around them as real in the sense that everything is interconnected.
Is it too linear?
Inward focusing tables are not about 'railroading' so much as they are about setting. The random table points to the interconnectedness of the world. The main plot, the major events, the big concepts, they all supported by multiple interconnected and smaller encounters. So a kingdom doomed to fall into revolution has a lot of interconnected parts and vignettes that can be shown through the encounters of a random table. The player’s still have a lot of control over how they respond to these encounters and what position they want to take on the themes.
Therefore, a good random table has encounters that relate to the details of the world; the plot threads, the political factions of the world, the ideas and philosophies, what people eat etc. For most linear stories answering these questions is a waste of time. But these details are still important, and games are not linear media. What makes games interesting and powerful is the way they can explore the details.
These details can work when they are introduced to the players through a random table and explored at their leisure. Players get the control and the option to understand these parts of the world or leave them as just as they found them. This can let all the details in a world exist without burdening the players with them. The good random table tantalizes players with glimpses of the world's complex underpinnings.