Hi galaxy developers,
I have been exploring developing Galaxy tools, and I must say Galaxy is an incredible project!
As I understand, it is only possible to install tool requirements by declaring each of them at the <requirements></requirements> section.
Is there a reason why there is no option to provide the tool requirements in an environment YAML file? I think it will be much easier.
Another question is, I also see that there is no option to install pip tools, is this correct?
Really so much easier? I doubt it somewhat since a typical tool only has few requirements and there are usually other botllenecks than adding those few extra lines 
pip installs are not supported because they are not usually reproducible enough unless you freeze the entire dependency chain. It’s also fairly trivial to create a bioconda recipe for tools that just require a pip install and this increases the level of reproducibility a bit on its own and also allows people to build biocontainers for each bioconda build, which can then be used by appropriately configured Galaxy instances for a much higher degree of reproducibility.