For reference, by "effective data normalization / optimization / compression", specifically I am referring to some basic design principals and tips, including: using value list/lookup tables (vs. text fields directly in most tables) (as the built in Analyze Performance/Table wizards can help users to automate), avoiding repeated values in subsets of record fields (eg. Contact Info shared by Company/Project/Employee tables vs. inlined and duplicated, and Product.Category.Group vs. Product.Category+Product.Group), avoiding Calculated Fields (using Queries to auto-calculate), use of Inherited Values + Infrequent Overrides (ProductGroup.IsTaxable vs. ItemTax), avoiding sparsely populated fields (replacing Fax 1, Fax 2, Work Phone 1, Work Email, Company Address, fields with RecordID+Label/AttributeType+Value fields, in some cases), use of Lookups/Numeric Keys (vs. Text IDs), appropriate data type sizes (Byte/Integer vs. AutoNumber/LongInt/GUID, Single/Currency vs. Double/Decimal, Number vs. Text), enabling Unicode Compression for text fields, and occasional Compact & Repair (which can be automated).
Such basic data normalization (which can be assisted even by wizards built into Access) combined with support for up to 255 simultaneous user connections and one-click (even or even scheduled/automated) "Compact & Repair", together with the easy built-in ability to split/migrate/mashup data (whether across multiple Access databases, files, etc.), new & improved Linked Table Manager for managing those data source links, simplified "file copy" deployment, lack of licensing fees, ability to even exceed database and memory limits of SQL Server Express, lack of expensive licensing/hosting cost & complexity requirements ($7500+ licensing + hiring consultants for every minor change and ongoing IT maintenance/hosting) of SQL Server, and 10+x faster and lower-cost of development and maintenance, ubiquity (with nearly 1.2 billion installs and many millions familiar with it), and unique Excel-like ability to allow end-user editing (for rapidly changing business requirements, by subject matter experts like Analysts) nearly as easily as Excel workbooks – all together makes Access not just sufficient, but in many cases the only viable option for most database projects.
It's for that reason that, without Access, you would see millions more of the far-too-common massive 100-sheet spreadsheets with complex, tedious lookup & calculation formulas and copy-paste workflows (with no other database solution feasible or cost-effective, and with SQL Server as a backend-only half-solution) instead of "automated, user-friendly, drop-down editing, drop-in-folder-deployed, auto-calculating, fast, compact all-in-one Access database solutions."