It's not the case.
There are consequences to the proportion of some nucleotides, the most well-known being the GC-content[1], or proportion in a sequence of bases being G or C (G pairs with C and A pairs with T). There are benefits to a higher GC-content, like the sequence being more stable.
From this the obvious question would be why this matters, since you obviously can't replace an A-T pair with a G-C pair just to increase this proportion. Except that there are ways to do it… kind of. If you look at the codon table[2], you'll see that there are multiple ways to represent each protein encoded by a triplet of nucleotides.