Let's imagine: You want to read a ZIP file. Will you write your own reader? I seriously doubt it, as the work, stabilising, and security (random memory access as an example) would be issues. But let's think we are couraginous. OK, we read rather not so simple format and carefully read the binary. Now, will you write your own DEFLATE and Huffman coding? Again, a bigger doubt.
I would argue that if someone cares enough to reimplement ZIP, it would at worst be twice as hard to write a Pack reader from scratch with no ZSTD or SQLite. And for those serious people, reading a format that lets them store better and faster would be a prize that is hard to say no to. But I get your point, and if you are in a desert and need something to put together fast before going out of water, tar may be a good choice.