Shiva Linga is very ancient, in fact most ancient. From the form, you go to the formless, through the Shiva Linga. Shiva Linga is sacred.
There are many more things; I do not know why, what and all that. I simply do it and enjoy it because I like it. We cannot understand everything. So, move in life by knowing a few things, assuming a few things and embracing everybody with love.
It is not mandatory that you should do everything only after you understand them. We teach our kids that they should brush their teeth. At that time, we don’t tell them that not doing it will give them cavities. We just ask them to brush their teeth. But when they grow up they come to know that they would have had no teeth if they had not done so.