Mobile GIS data collection apps with Leaflet and PostGIS - Udemy

Cost - Even if your needs are simple many commercial applications require monthly per-user subscriptions, often in the neighborhood of $30-$50 per month. For 1 or 2 users that may not be much but with 50 users it quickly becomes cost effective to write your own.

Customizability - Commercial "non-programming" solutions tend to be one-size fits all. Although they may have some flexibility, it is not uncommon for many applications to need functionality that is not available.  Writing your own mean that if you can envision it you can implement it. Often you can implement it faster than you could in a "non-programming" solution even if it is available.

Real-time data access - The techniques taught in this course access a PostGIS database directly so that any changes that are made are available immediately to any other client applications whether they be desktop GIS like ArcGIS or QGIS, other web applications, or other client software such as a spreadsheet program, etc.  This also means that there is no time wasted transferring data from device to server, etc which may save hundreds or even thousands of man hours in large data gathering efforts and avoid a large source of errors.