MP3 to WAV does not give you the audio back
The conversion is reversible at the container level (you get a WAV file out) but not at the audio level (the WAV cannot contain information the MP3 already discarded). MP3 compression works by removing audio data the human ear usually does not perceive. That data is gone the moment the MP3 was created. Converting back to WAV just puts the compressed-then-decompressed audio into an uncompressed container.
That sounds disappointing but it is exactly what most use cases need. The reason to convert MP3 to WAV is rarely "recover quality" (impossible) and usually "make the file work with a tool that prefers WAV".
The audio editing use case
Most DAWs (Logic, Pro Tools, Reaper, Ableton) work better on WAV than MP3. Repeated edits, fades, and effects on MP3 in a DAW can introduce artifacts because of how the DAW handles the compressed source under the hood. Converting to WAV first gives the DAW uncompressed audio to work on. The starting quality is still bounded by the MP3 source, but the editing chain does not introduce further loss.
The hardware sampler and legacy software case
Older hardware samplers (Akai MPC, AKAI S-series, Roland SP-404) and some legacy DAWs accept only WAV or AIFF. Loading an MP3 directly is impossible. The MP3 to WAV conversion is the workaround. The sample quality is no better than the source MP3 was; you are just changing the container so the device can load the file.
Why we default to 16-bit 44.1 kHz
CD-quality is the standard reference and works in every audio tool. Higher bit depth (24, 32-bit float) does not recover audio information from the MP3 source but does give you headroom for processing. If you need 24-bit output, open the WAV in Audacity and re-export at 24-bit after our conversion.
If you actually want quality, find the lossless source
If your goal is the best possible audio for editing or archival, the right approach is to find the lossless original (FLAC, ALAC, or WAV) of the recording, not to convert from MP3. Bandcamp, Qobuz, and Tidal sell lossless downloads for most music. For voice content, ask the original recording owner for the WAV master if it exists.