Why is Normalization Necessary for Linear Recommenders?

Benchmark Model Rank Results
collaborative-filtering-on-amazon-bookRLAE-DAN#2Recall@20: 0.0762NDCG@20: 0.0630
collaborative-filtering-on-gowallaRLAE-DAN#1Recall@20: 0.1922NDCG@20: 0.1605
collaborative-filtering-on-yelp2018RLAE-DAN#3NDCG@20: 0.0587Recall@20: 0.0706
recommendation-systems-on-amazon-bookRLAE-DAN#3nDCG@20: 0.0630Recall@20: 0.0762
recommendation-systems-on-gowallaRLAE-DAN#3nDCG@20: 0.1605Recall@20: 0.1922
recommendation-systems-on-yelp2018RLAE-DAN#3NDCG@20: 0.0587Recall@20: 0.0706