1. Old software version: If the software version is old, EMA indicators may not be added to the indicator library. In the updated software version, new indicators may be added.

2. Low user demand: EMA indicator is a commonly used technical indicator, but not all traders use it. If the software developer thinks that the user's demand for EMA indicators is low, he may choose not to add it to the software.

3. Copyright: EMA indicators may be protected by copyright, and you need to pay to use them in the software. If the software developer does not purchase the copyright or license of the EMA indicator, it cannot be added to the software.

4. Technical limitations: Some software may have technical limitations, and it is impossible to add certain indicators or functions. This may be due to the limitation of software architecture or design, which makes it impossible to add EMA indicators.