I would argue the opposite for exactly the same reason. SAM is a simple text file, BAM is not. While the two are obviously related, I really don't think a question about sam files should be tagged as bam nor a question about bam tagged as sam.
To take a very simple example, consider a question like "How can I extract all reads mapped to chr1 from a sam file" and the same one for a bam. The answer for the sam could be as simple as
awk '$3=="chr1". It could be done with no specialist bioinformatics tools and just using standard *nix text processing utilities.
Granted, the same could be done for a bam file if we first pass it through
samtools view, but isn't that like saying that a PDF file is the same as a text file because I can pass it through
pdf2txt or similar utilities?
Finally, I would argue that these are two of the main formats used in NGS analyses and each have their place and are used by different downstream programs and in different ways. I don't see any benefit in merging these two tags and we might be losing some "resolution".
Perhaps we can revisit the question further on down the line when we've seen how the tags are being used?