Static symbols make smaller files because they all refer to a single symbol that is stored only once in the file, change that symbol and all instances will change.
With Dynamic Symbols you have more editing flexibility, you can have more variation within the instances of that symbol. But these instances are all stored individually in the file, making it much larger.

No, no, no. The very idea of using Symbols is to being able to reuse them.

Better yet just make those settings the user can select and set their own defaults. I use almost exclusive dynamic and would be equally sad if that wasn't my default. I totally vote for the option to set our own defaults in symbol creation.

Amen. I constantly create static symbols in my workflow and it feels annoying to have to select "static" every time I need one. On top of this, It's impossible to create a macro where a symbol is created with the "static" option because it isn't record.ed.

I think this should be an option in settings panel so that users could choose the functionality they prefer.

Ditto. New features and tools are brought to the forefront in Illustrator to force us to use them even if it hurts our workflow. This is beyond aggravating for one who works in Illustrator much of the day and must be efficient. Why would a software developer want to make users' work more difficult? Please fix this.

Also, why in the world does symbol type default to Movie Clip?

Yes, 9-times-out of-10 I want a STATIC Symbol. Please give us the option to work more efficiently instead of changing work habits because an Adobe programmer likes a new feature.

I would also like to be able to set the default as static, since copy with "Optical" kerning changes letter spacing non-proportionally at different scales. I would think it would be better to allow us to choose what we'd like as default, as dynamic may work just fine for some as the default.

When the dynamic symbol instance is deformed, the result changes depending on the setting of "Scale Strokes & Effects", and Users switching this setting are confused.
Moreover, adding one anchor point to the master symbol will reset the appearance of the instances.

Dynamic symbols are an interesting feature, but we need to be careful to use them.
The default should be the static.

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ダイナミックシンボルのインスタンスを変形すると、「線幅・効果を拡大縮小」のチェックの有無によって結果がその都度変わります。設定を切り替えながら使っているユーザーほど混乱するでしょう。
さらに、マスターシンボルでアンカーポイントをひとつ追加しただけでも、配置済みのインスタンスのアピアランスは強制的にリセットされてしまいます。
ダイナミックシンボルは面白い機能ですが、使うには注意が必要です。シンボル作成時のデフォルトはスタティックであるべきです。

And dynamic symbols are still very buggy.
https://illustrator.uservoice.com/forums/601447-illustrator-bugs/suggestions/34615957-dynamic-symbols-don-t-move-when-direct-selecting

Being able to change the default symbol type to 'Static' instead of 'Dynamic' would be great. Dynamic symbols can cause scaling issues here and there's never a case where my team WANTS our symbols to be dynamic.