Well, I don't think that anyone claims that it doesn't work, and I don't think some packaging system is a good comparison. I mean, email effectively has been us

Well, I don't think that anyone claims that it doesn't work, and I don't think some packaging system is a good comparison. I mean, email effectively has been using SRV records (even if they are called MX records in that case ...) for three decades, so obviously it works. But it commonly requires an additional round trip for (initial) resolution, which adds delay, which is kindof relevant for interactive use, not so much for package managers or SMTP. Also, you as the site operator can't really do anything about how recursive resolvers handle additional section data (and there are millions of them deployed on crappy home routers with probably equally crappy DNS software), in contrast to out-of-zone glue, which is something completely under your control. That being said, I don't think it makes sense to not standardize it for mandatory client-side use with HTTP, (a) because network latencies are not exactly increasing, even mobile networks are moving towards single-digit millisecond RTTs, and (b) browsers could just be backwards compatible, and issue SRV, A, and AAAA queries for the URI domain name at the same time, so you would only need one round trip to figure out the addresses of sites that don't want to use SRV, and you'd only get a negligible amount of traffic for one additional DNS request without any additional latency.