cooking dried legumes

The variation of cooking time is simply based on the specific plant. Legumes have an outer skin around a starchy center. This protects what is essentially a seed (and only when they are in the right environment with sufficient water will they start to germinate). To soften, water has to permeate the skin and get inside the seed, giving us the soft mushy inner part after cooking.

The rate at which this happens depends on a few factors, the thickness of the skin being one of them. Ph level of the water can also be a factor. As a rule of thumb, true beans with their thick skin need a long time to soften, peas (whole) are kind of in-between and the thinner-skinned lentils or chickpeas are amongst the fastest. From a culinary perspective, removing the skin (often done for red or yellow lentils) or opening up the seed (split peas) will change the time significantly.

You may also want to consider that while the legumes (fabaceae) are related and occasionally used interchangeably in cooking, they are diverse enough to have different physiological characteristics, so that soaking and cooking times have to be adjusted. (This Wikipedia entry on “beans” gives a nice overview.)

And lastly, storage time can be an factor. While legumes can be stored for a long time (often multiple years), the skins will get tougher and it can get difficult to get very old beans to soften up at all.

Just like Stephie, I believe that the largest factor here is simply that there is no single recipe that fits all legumes, and that you have to use different times for different plants.

But I also wanted to point out a second factor influencing your observation. Many people prefer their legumes very soft, and work from a "more is better" attitude. Even if chickpeas are edible after some minutes, they are much creamier when you cook them for a couple of hours, and this is considered a plus by many eaters. On the other hand, undercooked legumes are frequently considered unpleasant, so cooks prefer to have a good-sized time buffer against such an occurrence. Then there is also the problem with too-old legumes: they never grow soft, but people sometimes mistakenly think that they are undercooked instead of too old, so based on these experiences, they tack on extra cooking time on their legume recipes, "because last time I boiled it for X time and it wasn't enough". And then, note that traditional recipes come from kitchens in which there was always a fire going, so holding the pot longer was not causing any additional cost or inconvenience, and even today, there are only a few cultures where cooks are interested in shortening cooking time.

These factors together combine to recipes where the recommended cooking time is considerably higher than the minimum sufficient cooking time for legumes, and if you are accustomed to check for doneness and turns off when ready, you might have noticed the discrepancy, while others just follow the recipe and don't give it a second thought.

You don't really need a recipe for this you cook it for as long as it takes to get to the consistency you like and then you spice it like you want it to taste. One thing people who are new to legumes don't realise is that if you add salt or acid to it when it cooks you can cook it until the rapture comes but it will never be soft.

Salt leads to cooked and hard beans. Something which is akin to chewing on car tires. Same for any citrus. You can add spice but make sure it does not have salt in. You are probably best served to just cook legumes in water and when it is soft add the flavour at the end. It really is a very good neutral tasting plant protein. You can flavour it really just like you want.