If I’m fed up with my marriage. Can’t I just walk out of it instead of filing a divorce suit in court?

No. The marriage must be formally dissolved in court. If not, the marriage remains intact. Any spouse who enters into another marital relationship, in such circumstance, commits the crime of bigamy[1].

[1]. It is a crime which is committed when a married person under the Act enters into another marriage with another person, while the first marriage is still intact and in the lifetime of the other spouse. Bigamy is discussed in greater details below in the book.