There are gazillion adults who took piano lessons as a child but stopped playing for various reasons. Some aren't the least bit interested, but many wish to return to piano playing at some point in their lives.
I have never heard anyone express relief that they didn't learn how to play piano, but I have heard many people say they regret that they didn't make the most of their childhood lessons. Many people with those regrets suffer from the "round-to-it" problem--they'd love to relearn piano as soon as they have time to get "round-to-it." And of course no one wants to sit in old-style classes with a silver haired grandma who couldn't tell rock n' roll from a rock. In addition to that, their busy schedules would only prevent them from attending the piano lessons regularly.
So what's the answer?
There are two connected factors that create an unprecedented opportunity for these type of adults.
Firstly, the internet has opened up opportunities and information for everyone. Up until this decade people were mostly limited to a piano teacher that was in their region. But it's not true any longer. A lot of piano teachers today have branched out into the online world by offering lessons on the internet. Some teachers will supply various media to help learn to play whether you are a beginner or an advanced improvisational player. And they are simple to find as well. Typing phrases about piano playing into Google or other search engines will return a wide variety of interesting results. (Attempt it, and see the results!)
The next thing is one that was already there, yet until recently has not been exhibited well enough for a layperson to digest. Basically, there are three methods for learning to play piano, and combining elements from the different techniques can produce better results than relying on just one method.
Those three methods are:
(1) Playing from a copy of the printed music. More than 95% of piano lessons are based on the ability to read sheet music and to make your fingers do what your brain wants them to. This is the traditional approach to piano lessons; featuring repetition of scales, drills, finger exercises and continually practicing pieces from the most basic to advanced compositions.
(2) Playing without the need for sheet music. Some rare people can truly play songs "by ear" and they don't need any instruction since they can play any song they want easily. You can learn some techniques to play by ear, but don't fool yourself into thinking you'll be playing like a pro in no time. However, most people will find that they can be taught the method to play a song by ear, thus, learning how to play well enough to entertain for company.
(3) Using chord symbols allows you to play the piano. Numerous expert pianists - particularly those that play jazz - use lead sheets. Fake books are musical books that contain their songs in a "lead sheet", which contains just the musical melody and the concurrent chords for the song. This kind of piano playing requires you to learn at least some chords and you will need to understand how to read music in the treble clef, which is much easier to learn than both bass and treble.
This type of piano playing does exist and is accessible to all, even though most view it as a style limited to professionals. This isn't so. It's a simple method that can teach you an appreciable amount relatively quickly. In just a few weeks' time, you can play the piano well enough that you'll be proud of your playing and want to play for your friends.
These techniques are all feasible and can be learned using piano teachers online. The most effective thing to do is to combine all three - learning to read music, developing an "ear", and learning the chords and how to use them to create music.
It doesn't matter which method you choose - just choose one and begin. It will boost your self confidence and entertain you at the same time.