The reasoning is that it will be very helpful. Kanji can be written out on a keyboard and you probably won't need to study them hardcore since you only need to know maybe less than 100 of them to get by on a daily basis such as signs (entry/exit etc...). You can survive without kanji! But the same cannot be said with kana. Kana is used everywhere, it is the bare-bone necessity.

If you want to buy a cup of ramen, you will need to know how to read ラメん. Of course, there will be a picture of ramen noodles but what if say, you want to eat at a ramen stall?  It could be ラメん or it could be anything else. Knowing from a distance will be very helpful particularly if the shop owner cannot speak a lick of English.

Additionally, writing phonetically using latin characters doesn't have the same result as kana. What if you read something that uses a singular o instead of ou or o with the line over top of it? How can you know how to pronunce certain words since romaji is so weird and not normalized? Sure, there are various standards but these standards can intermix depending on the writer and overall it is just a mess.

So please, do yourself a favor and start learning both Hiragana and Katakana!  After just 1-3 weeks of studying, you will know them all! You can even do it simple by learning 5 kana per day. This is a reasonable amount and not too much to overburden yourself with. Take a month to familiarize yourself with both Hiragana and Katakana. Get to the point where you can read kana subtitles on things like music videos. Trust me, this necessity may seem annoying but long-term you will be learning things at a much faster rate and you will have begun with practical Japanese.

So where should you start?

You should start here:

https://www.jappleng.com/education/course/overview/1/jplearn