First and foremost, it comes down to the popularity of the source material. FFVII was a massive success all around the world while Trials of Mana was only released in Japan.
Pretty much this.
As well, of the Mana series, the most popular one is Secret of Mana which Square already took at shot at it 2 years ago. It didnt get rave reviews but my friends and I still very much enjoyed this.
Also the Trials of Mana remake removed coop so that was a let down for me.