It's Dangerous To Go Alone!

Turn-based RPGs can vary greatly in terms of game mechanics, but most have at least a few common elements. They tend to require you to think carefuly about your decisions and to use your party member's varying strengths to the fullest potential. As you can imagine, the most difficult and least enjoyable parts of the game tend to be when you only have a single party member. I will provide a general analysis of this trend, and may later take closer looks at individual games.

The first and most obvious reason is that there's no safety net. If your only character's HP falls to 0, the game is over. Few early game enemies present much of a challenge, but if they attack in groups, your character is unlikely to be able to withstand the enemy's assault for long unless the enemy misses often, or you can kill them in one hit. Some early game enemies can inflict status effects that cause you to lose control of your character (sleep, paralysis, confusion, etc.), and the battle can quickly turn against you if you don't remove it quickly, something that may not be possible with the items and skills at your disposal.

Your first character generally has few tactical options, since it's most common for the game to make your first character a warrior with strong offense and defense but no magic. Said characters are generally ideal for fighting alone, since they are somewhat resilient and have good offense without having to expend mana or other resources, but in many cases, they will lack abilities that can strike multiple targets, hit enemy weaknesses or do more damage than usual. As a result, many boss battles boil down to battles of attrition; the player generally attacks until their health drops low enough that they have to heal, a process that repeats until one of the two combatants is dead.

There are many situations that make it obvious how limited you are with only one character in a party. When your health drops low in the middle of battle, every turn you spend healing yourself (usually with an item) is one less turn that you will be able to go on the offensive. In most encounters with multiple enemies, your chances of victory are slim unless you're able to defeat each foe within one or two turns. The reason for this is because all of the enemies will focus their attacks on your protagonist until that character is dead, as opposed to dividing their efforts between all characters who are still alive(or focusing on a character that is drawing their attention). It's no exaggeration to say that in many games, the early game can be more difficult than the late game in some ways.

So why put players through this? There are a few reasons. From a gameplay perspective, it can keep things simple at the outset of a game. As long as the foes are easy enough to defeat that you won't necessarily need to use items, spells or whatever help another party member might offer to win, you may not mind having only one party member at your disposal. Super Mario RPG is a good example of this, since Mario is able to handle himself fairly well on the road to the first town.

There are also narrative justifications for limiting you to one party member. At the start of the game, it may not be time to meet your other companions. Later on in the game, there may be cases when the protagonist is separated from the rest of the party for some reason or another, such as when Cecil's ship from Fabul to Baron is wrecked, resulting in him washing ashore near Mysidia and eventually becoming a Paladin.

Of course, while there can be times when it's best to limit the player to a single party member, these sequences shouldn't last too long. In most party-based RPGs, managing your party well is an important aspect of the gameplay, and the cast's relationships with each other are an important aspect of the story. There may be times when the hero must go alone, but the story and gameplay are best when the party is together.