Sodium & potassium silicates have it over sodium and potassium carbonates for many reasons when it comes to laundry detergents.
Silicates have slightly higher pH than carbonates but less than sodium hydroxide. In terms of soil suspension and removal properties, wetting, and rinsing silicates beat washing soda.
https://www.texfinity.com/dynmedia/0fff7da2ad3ecf9f3422cf8171c7d8b6
Besides functioning as source or alkali on wash day silicates also work as a builder as well. Silicates are likely closer to one thing out of a box that could replace phosphates as it comes.
Fritz Henkel's first "detergent" Bleich-Soda (bleach soda) made from sodium silicate and calcined (water-free) soda. It promised to whiten and clean linen without harsh bleaching agents (read eau de Javel/chlorine bleach).
https://www.antiquariat-kastanienhof.de/images/product_images/popup_images/s40320_3.jpg
What Henkel got ahold of there was one of first laundry "breaks". Alkaline pH in water of silicate and soda when combined with hot (or boiling water) broke soils and muck from textiles. Via water softening properties soap reside would be leached out of fabrics and settle into water.
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This step was important as soap was still queen of wash day. Presoaking or prewashing with an alkaline water bath in addition to above mentioned things also reduced the acidity of textiles (from coming into contact with human bodily fluids) which in turn would make job of subsequent washing with soap easier.
Henkel's later invention "Persil" built upon previous bleach-soda formula in that it contained soap, silicate and perborate. A remarkable combination when used property at high temperatures was more than capable of producing quite clean and white laundry. Most tellingly Persil did not contain soda IIRC.
Henkel loved themselves some silicates because they came out with yet another product based upon them; "Sil".
Sil today is a spot/stain remover, but its original incarnation was perborate bleach and silicates. One took wash that had already been done (usually boiled) using Persil (soap and silicates), then boiled them again in this "bleaching" rinse. Containing more bleach but no soap this treatment would remove stains, treat yellowed fabrics and remove other discolorations that survived the wash.
When using soap for wash day first rinse is usually in hot water or things were boiled, so there you are.
For generations at least in Germany above brought about the Holy Trinity of wash day of Henko, Persil and Sil.
Introduction of Sunil and later Persil 59 put an end to that holy trinity. Once soap was replaced by detergent all that presoaking and boiling afterwards was largely not required.