As for WHY was this default chosen, it's because it's easier (or at least it was) to read adjacent content by considering the end of each cell. This comes from old accounting books, see example below, you'll see the amounts are at the baseline of the content of left column (which is multiline).
- Why does the text go to the bottom of the cell in Google Sheets?
- Why is my text at the bottom of the cell in Excel?
- How do I remove the bottom alignment in Excel?
Why does the text go to the bottom of the cell in Google Sheets?
Text alignment
By default, any text entered into your spreadsheet will be aligned to the bottom-left of a cell. Any numbers will be aligned to the bottom-right of a cell. Changing the alignment of your cell content allows you to choose where the content will appear.
Why is my text at the bottom of the cell in Excel?
By default, Microsoft Excel aligns numbers to the bottom-right of cells and text to the bottom-left. However, you can easily change the default alignment by using the ribbon, keyboard shortcuts, Format Cells dialog or by setting your own custom number format.
How do I remove the bottom alignment in Excel?
Undo alignment changes
To remove an alignment change immediately after you apply it, click Undo. To make alignment changes later, select the cell or cell range you want to change, and click Clear > ClearFormats.