I'm not willing to say there is no standards. There's no standard if one wants to ignore them, as much as there's no standard in web development or any other profession then. If you speak to a print/prepress designer, they know the standards and it's anything that is the most compatible with the postscript technology and that will render the best print quality possible. So it's not a matter of preference, it's really a matter of results.
With the web popularity of web development, and the split between print and web design, maybe the "standards" are being questioned though. Not all designers have the same priorities.
What's smart in design is to be as compatible and practical as possible, and be WYSIWYG (what you see is what you get.) To anticipate the future use of a logo, the same way the conception of the design itself is based on creating a logo that will look good in any situation, for a long time and on any medium.
As to why a vector format should be included, that's a bit like asking why a builder should build a house with bricks instead of vinyl siding. Both are nice, they protect your house but given the choice, anyone would go with the bricks because it's flexible, solid, easy to repair and a pretty good long term investment. The bricks in logo design are vector files. It simply makes sense that a logo that cannot suffer of any degradation of quality, that can be converted and modified easily, use for pretty much anything, and is the most flexible format will be the best choice. Of course you can be satisfied with a 40" width PNG or JPG file, it can work too but it's not ideal, and not ready to use for all situations.
As I said below, if I have the choice of one file to provide as a logo, it would be a vector PDF.
But frankly, why not simply give more options to the client and provide many formats.
I previously explained below why I provided all the files.
A good designer will provide you these things when you purchase a logo:
1) A set of vector files: .ai, .pdf, .eps, .svg
This way the client is free to use his logo on any project and share them with other designers who might need them. The vector are the best quality that exists and the favorite of all. They can be resize without limit and without loss of quality.
2) A set of High resolution files: .tiff, .psd, .png, .jpg
This will be a rasterized set of files in high resolution (preferably 300dpi and at least 6" width) that the client can freely import in his own document (eg. Words, Powerpoint) for his own print projects.
3) A set of web files at 72 dpi of different sizes: .jpg, .png
The designer will provide these files so the client can use them freely online, on social media, on profiles, etc. It's good to provide these because the client won't need to resize the logos himself and that's also the best way to provide logos that are already optimized for web, in the best quality possible... with and without transparency.
4) A separate JPG information sheet with the color values, recipes and versions of the logo as a reference. On this will be written which pantones colors were used, the CMYK and RGB values of the colors, what are the files provided, some instructions on when and how to use the files mentioned above and the contact details of the designer! I suggest using a JPG but it could be a PDF. JPG are simply the most compatible of all and give a good preview of the logos with any specific software, unlike PDF.
5) In addition, a black and white version of the logo can be provided in all the formats mentioned above. But that depends on your agreement on the project.
6) If the logo is intended to be used for printed projects or special use, it should be created accordingly. If the client needs a logo easy to print and is provided with a graphic in full colors, full of gradients and shadows, then it's not right. If the work needs to be use for cheap printing, then a 1-2 color logo should be created, if it's for web and will be used at small size, then the text should be clear and the graphic should be clear even if resized very small, etc.
But if there is ONE single file that should be provided, I would say PDF in vector; at least this format can be opened by pretty much anything. An .ai cannot be opened by older version of Illustrator if created on the new ones and cannot be imported in some publishing or design software.
Suggestion: Here is how the folder with the logos should look like. They should sorted to help the client; they don't always know what is a vector and what does what! But if they're asked for a vector and see the logo well identified, they can find it easily!