Why isn't steganography the ultimate way of sending secure data ?

I've recently coded a steganography program to hide text in image. It's very simple, you input your text which is internally converted as an array of bytes (concatenation of the binary represenations of the ASCII values of each character in that text). I then loop over each pixel and change the LSB of the green color to match the current byte at the iteration.

Long story short, I'm thinking about it again and I'm wondering, why isn't steganography more widely used ?, first of all you can very easily hide that data in seemingly common material (eg everyday life images), but even if someone was to analyze deeply the image and know there is something hidden, how can he uncover it as long as you use your own algorithm ? I mean, the possibilites are endless, you could choose for instance to hide alternatively the bytes in the red colour of a given pixel, then to hide the next byte in the blue, then hide two bytes in the last two bytes in the green, etc.

I think I'm wrong because otherwise steganography would be very used, but I'd like to know why steganography isn't widely used. Thanks.

(Btw: first time posting in this sub, I hope it fits the rules as they seem pretty strict)